The third book of Aristotle's Politics is focused on citizenship and its merits, and from early on it provides enlightening information about the benefits of citizenship:
[Aristot. Pol. 3.1274b] But a state is a composite thing, in the same sense as any other of the things that are wholes but consist of many parts; it is therefore clear that we must first inquire into the nature of a citizen; for a state is a collection of citizens,
[Aristot. Pol. 3.1275a] so that we have to consider who is entitled to the name of citizen, and what the essential nature of a citizen is. For there is often a difference of opinion as to this: people do not all agree that the same person is a citizen; often somebody who would be a citizen in a democracy is not a citizen under an oligarchy. We need not here consider those who acquire the title of citizen in some exceptional manner, for example those who are citizens by adoption; and citizenship is not constituted by domicile in a certain place (for resident aliens and slaves share the domicile of citizens), nor are those citizens who participate in a common system of justice, conferring the right to defend an action and to bring one in the law-courts (for this right belongs also to the parties under a commercial treaty, as they too can sue and be sued at law,—or rather, in many places even the right of legal action is not shared completely by resident aliens, but they are obliged to produce a patron, so that they only share in a common legal procedure to an incomplete degree), but these are only citizens in the manner in which children who are as yet too young to have been enrolled in the list and old men who have been discharged must be pronounced to be citizens in a sense, yet not quite absolutely, but with the added qualification of ‘under age’ in the case of the former and ‘superannuated’ or some other similar term (it makes no difference, the meaning being clear) in that of the latter. For we seek to define a citizen in the absolute sense, and one possessing no disqualification of this nature that requires a correcting term, since similar difficulties may also be raised, and solved, about citizens who have been disfranchised or exiled. A citizen pure and simple is defined by nothing else so much as by the right to participate in judicial functions and in office. But some offices of government are definitely limited in regard to time, so that some of them are not allowed to be held twice by the same person at all, or only after certain fixed intervals of time; other officials are without limit of tenure, for example the juryman and the member of the assembly. It might perhaps be said that such persons are not officials at all, and that the exercise of these functions does not constitute the holding of office; and yet it is absurd to deny the title of official to those who have the greatest power in the state. But it need not make any difference, as it is only the question of a name, since there is no common name for a juryman and a member of the assembly that is properly applied to both. For the sake of distinction therefore let us call the combination of the two functions ‘office’ without limitation. Accordingly we lay it down that those are citizens who participate in office in this manner.
Aristotle's definition, "a citizen pure and simple is defined by nothing else so much as by the right to participate in judicial functions and in office", highlights the main benefits of citizenship, participation in the commons. This didn't only translate to a right to vote, but more importantly the right to actively participate in all forms of government, the key characteristic of the Athenian Democracy being its extremely high level of participation. Any willing citizen could propose, debate and contest (in court) laws, and act as a juror and a prosecutor.
Citizens were generally held to a higher status than non citizens in judicial matters, and were not obliged to produce a patron in court. In contrast, metics were required by law to have a guardian/sponsor that would stand for them, and failure to produce a guardian would mean they would lose their property and be sold as slaves. In general, masquerading as a citizen would lead to prosecution and punishment. Aristophanes The Wasps revolves around its protagonist, Philocleon, being (falsely) accused of not being Athenian and barely escaping convinction. Aristophanes himself might have been accused of xenia (being a foreigner) by Cleon, a statesman often caricatured in the comic's plays.
One important benefit available to all citizens was the honour of financially supporting the state (yes, at the time it was considered an honour ;). Contributing to the state was exemplified by liturgies, voluntary public services that were practically limited to the richer citizens.
As for Pericles' reforms, in 451 BC he introduced a law that reduced the number of citizens, stating that only the offspring of two Athenian citizens could be citizens, and Aristotle theorized that the law was a natural consequence of having too many people sharing the benefits of citizenship:
[Aristot. Pol. 3.1278a] Nevertheless, inasmuch as such persons are adopted as citizens owing to a lack of citizens of legitimate birth (for legislation of this kind is resorted to because of under-population), when a state becomes well off for numbers it gradually divests itself first of the sons of a slave father or mother, then of those whose mothers only were citizens, and finally only allows citizenship to the children of citizens on both sides.
As Felix Goldberg already mentioned, compensation for participating in the Boule was instituted in the mid 5th century, and Pericles' reforms allowed payment for jurors in the Ecclesia. Aristotle is thus probably correct, and Pericles intend was to minimize the added cost for the state by reducing the number of people who could participate in the two bodies.
Pericles' reforms also shifted the family dynamics of the era, Athenian men were limited to marrying only Athenian women, or their children would not be citizens. In the 4th century what was until then a practical limitation became law, as Demosthenes describes in Against Neaera:
[Dem. 59 16] If an alien shall live as husband with an Athenian woman in any way or manner whatsoever, he may be indicted before the Thesmothetae by anyone who chooses to do so from among the Athenians having the right to bring charges. And if he be convicted, he shall be sold, himself and his property, and the third part shall belong to the one securing his conviction. The same principle shall hold also if an alien woman shall live as wife with an Athenian, and the Athenian who lives as husband with the alien woman so convicted shall be fined one thousand drachmae.
Ironically, Pericles apparently pulled a few strings and managed to get his illegitimate son with his Milesian mistress, Aspasia, recognized as a citizen and as his heir. Pericles the Younger went on to serve as a general in the Athenian army (an honour reserved only for citizens) and was executed for failing to pick up survivors in a storm after the Athenians' defeat in the Battle of Arginusae.