From my opinion...

PSP is for you if...
1. You are rich... plenty to spend for UMD games
2. You are poor... but want to play Hacked games... which is no no...
3. You want a nice and super handheld console machine.
4. You want to play homebrew emulators games... but hacking fireware still no no...

Nintendo DS
1. You want to chit chat using wireless connection.
2. You want to play lots of nice games.. GBA/GBC/GB/NDS
3. You like cute games... and your small little nephews will love to play these cute games..

GamePark Holding 2x (GPX or GP2x)
1. You like linux fans.. like me..
2. You like open source..
3. You like homebrew emulators.
4. You like to write portable applications/games..
5. You don't want to spend RM hundreds to buy games
6. You still have lots of Rechargeable AA batteries... ( i got 8x2500 Mah )

Gizmondo - There's not much games now.. many later...

I currently use GP2x ... a lot of open source community are working on homebrew stuff... 1 or 2 months since released .. almost all homebrew emulators already ported...

Visit http://www.gp32x.com

PSP wireless multiplayer is cool... but drain battery too fast...

USD 169 from play-asia... its about RM630 (3.7 conversion)
RM170 for Courier

So all together is about RM800+

Play-Asia give u USD 5 voucher... and a packet of Sweet...

I'm still waiting for them to restock the tv-out cable... USD 9.90 ...

For Courier i use UPS ... 4 days only from HongKong To KL...

Most of the development people in GP2X came from GP32 and Tapwave Zodiac...
And they all are retro gamer...

Latest GNGEO plays Metal Slug 5 (Neogeo MVS)... i heard...
Support Open Source.... stop piracy ...

Currently firmware 1.4 has been released..
Source code for the kernel.. 90% of it has been released... due to divx license problem.. the mplayer source code not release yet...
the development team are working on the second processor (arm9 940t)....
Once they found out how to take advantage of the second processor, then emulator will be speed up..
gp2x is only for hardcore linux people and retro gamers...
cyclone 64k have been ported to arm.. so sega genesis and neogeo cps1/2 in gp2x beat psp mips ... currently

But gp2x lose out on nes,snes and gba... because of specialize chip... need arm asm code for this chip.. then will be full speed...

CPU speed for gp2x can be overclock until 300Mhz (varies between each gp2x).. so two processors ... is about 600Mhz in total..

Stable...? Ya.. it serve its purpose... ffmpeg support...

GPH is currently open sourcing the gp2x kernel... so development is just started..