Are the psp emulators good enough to play most games?
No experience with playing PSP on a computer, but the official emulator/compatibility layer on PS3 does a passable job, and Vita/PSTV have perfect virtualization
And if i do choose to buy a psp which model is best?
There are no truly bad models, but the key features of different models are:
1000 and early 2000 series - unbrickable
1000 - infrared port
Anything except 1000 = 64MB ram (used by a few plugins and homebrews, mainly emulators)
2000, 3000, N1000 = Go - video out
Anything except Go - affordable storage via microSD converters, standard miniUSB data port and commonly available charger
Go - folding and compact, Bluetooth (with video out and a PS3 controller it makes a fine portable PS1)
1000, 2000, 3000 - easily replaceable battery (not like there still are any excellent ones on the market), brightness and mute physical buttons (convenient for homebrew plugins)
3000 and E1000 = Street - brightest screen
anything except Street - stereo sound, autobooting CFW
very strongly debated - best screen
none - good range or WPA2-compatible wifi
My choice is an early 2000, but any model will do its job -- playing media and games