Should i keep my old phone or get a better used phone?

i have a samsung m300 and i love it but my cousin has a samsung a900 and he needs to get a new phone and he may give it to me but its used. the samsung a900 is better than the m300 bcuz it has an mp3 player (which i want), better camera that rotates (so cool), bigger screen, it can work with the mosquito ringtone, and its thinner.
all those things are things i want with a phone that i dont have
the problem is that the phone is used and the keypad is sorta bad looking but it works. i think i may be able to fix the keypad but idk. also some marks are able to be seen but the actual phone works great
so should i get it or keep my old phone?

Get the new one, but keep your old one just in case!

if you have had your account more than two years, call your server and tell them your having trouble with your old phone and can you get a NEW ONE FOR FREE or a small charge.
i have this several times over the years and have received both free and small charges for a new phone.
most will do it but you'll have to agree to a new 2 year subscription.
remember to tell them your having trouble with the old phone.
cuts out, hard to hear. battery goes dead to quickly.
good luck to ya.
i have at&t used to be cingular.

get the new one its cooler. :) but the chocolate cools