As with everything, always good to keep the goal in mind: What do you want to do - play games?
Fat PS2 models can take a hard drive, so you can take all your games with you by just carrying around the PS2 and using Open PS2 Loader to load the games from the hard drive. The only problem is to get the games on the hard drive, you have to unplug it from the network adapter and plug it into your PC.
Slim PS2 models can’t take a hard drive so you have to boot games over the network, so you have to carry an ethernet cable and the additional computer if you want to bring it to a friend’s place. You can use a Raspberry Pi but I prefer to use an old laptop. Built in battery, screen, keyboard, and I can have GameFAQs open on the laptop while I play on the PS2! Plus, if I want to try a new game, I just drop the ISO into the folder. The Slim is small, runs very cool, and replacement laser units are easy to find. The only problem is the cable mess taking up more space than the PS2 itself.
|SCPH-10000, SCPH-15000, SCPH-18000||V0||Asia only|
|SCPH-5000x||V9-V11||IR receiver built-in, iLink port removed. V9-V10 motherboards could drive too much power to the laser if it can’t find anything, requiring the “diode fix”|
|SCPH-7500x||V14||IOP replaced with Deckard, slightly worse PS1 compatibility|
|SCPH-7900x||V16||Weight reduced from 900g to 600g|
|SCPH-9000x||V17-V18||incompatible with FreeMCBoot, still moddable via Fortuna; integrated power supply raises weight to 720g|