well, here's the deal.
1. if u have a budget of 20k n don't care about the remaining 1000000000000000000 Rs. u wanna spend on original games, then PS3 is the answer. If u don't want to spend the remaining 100000000000000000000 Rs. on originals, xbox 360 arcade comes for 12k n can b modded easily, so u can run "backups" of "ur" games on it at a price which im pretty sure is much lesser than mentioned earlier
2. If u want better graphics? Ps3 is the answer as compared to 360 but der is maybe a difference of 0.0013 between them.
IMPORTANT - I'm pretty sure both the consoles are gonna get outdated within 2 yrs max, so if I were u, or in this case, ur friend, I would purchase the cheaper alternative.
IMPORTANT 2 - read somewhere that Sony is coming up with a USB hardware upgrade for the Ps3 to make it a next next gen console. If that is true, then I would go for the Ps3 (cuz next next gen xbox would cost a bomb). But then, it might be a rumour, so you will have 2 check up on that. Cheers!