if you ever get an urge to pick a DS, pick a DSi and a flashcard, no need to do any fancy upgrades or crap, just drop 'n drag homebrew, a DS by itself is a very lame toy, but with the flashcard you can play ROMS, you can access internet, messenger services, IRC, mail services, notepads, drawing apps, wardriving software and so much more
the PSP can do that as well? well, sure
but who has a highly responsive touchscreen? :B!!!
i'm a nintendo fanboy, but lets see, I'll be as the facts go:
Graphics engine/Sound:
PSP wins obviously, we are literally comparing a portable PS1 vs a N64, and the PSP has widescreen, kickass for movies
and let's face it, Sony is good at what it does, while the DSi has a built in media player, it will never sound as good as the DSi, and the PSP plays mp4 files effortlessly while the DSi seems to have a bit of a lag with them
Durability/Comfort
DSi takes it, nintendo products are just like that, and what with the self-folding design, the screens are well protected, the touchscreen is incredibly tough, and the device itself can stand a lot of falls
there are gimmicky games, there are 'ported' games for the PSP that have uncomfortable button layouts, there are gimmick games for the DSi that abuse of the stylus, but in general, in 'good' games with clever design, it's a tie, -however- with me being a RPG fan, the stylus has WAAAAY too many advantages and offers very creative and unique puzzles, and since we are talking about confort, it's easier to keep eyes on battle screen -and- tap weapons on lower screen than to pause and select
when browsing/chatting/writting stuff, the DS takes the cake, I hate writing stuff on my PSP
Library:
always evolving, always changing, both excel, a fair tie
the PSP has lots of fluff games, so does the DSi
the DSi has lots of smash titles, so does the PSP
personal opinion? I'm 27, I love studying japanese, drawing and I have a nephew and a niece, I bought a DS and a DSi to them, I couldn't be happier
the DS has games like 'my english coach' 'my japanese coach' and the 'Big Brain Academy' series, you can practice writting in the 'coach' series, making the learning process very dynamic, the DS has a built in microphone so you can practice your pronunciation, and the 'brain' series, well, ffs, my niece is 5 and half, yet, she is about to grasp the concept of multiplying, yet, her school friends don't even know how to count :I
and with applications like Colors! or DSO irc, I know I will always be amused
and really what does the PSP offers to -me-? only two games have caught my fancy, the homebrew is not very attractive to me, the reason I carry my PSP everywhere is because of the movies and music
Cost
DSi by far, the device itself costs much less than the newest PSP and with the DSi you just buy a flashcard and a microSD (wich are real cheap) and you're set, with the PSP you have to buy memory sticks, wich are unhealthily expensive
that said, on 1Gb, you can fit Six 'top tier' DS games, on the PSP, top tier games take 800mb, this translates into me having to struggle with the 2Gb memory stick that I could afford (down here, those cost $600p, roughly 55dlls) just to keep two games and a bunch of videos, while that on the DS I am packing a 8Gb microSD (down here, under 400p, roughly 34dlls) wich I have stuffed with over +15 -good- games, an entire music library and I still have +3Gb to spare