Vita:Vita Model Differences
Page content & researching collaboratively taken from io55.net's PS Vita page with permission.
There are four Vita models, of which only three are true portable game consoles.
Models
Models are arranged chronologically.
Vita PCH-1000 "OLED" with Wi-Fi and 3G (2011-2013)
The fullest-featured version of the PS Vita. Easily identified by it's oval-shaped PS, start, and select buttons, heavier and thicker body, plus a SIM slot on the left side for this version. Featuring an OLED screen, a proprietary charger, and no built in storage, the biggest reason one would prefer a PCH-1000 is for the OLED panel + SIM slot pairing the device features. The OLED screen adds a color depth and screen quality not found on other models, while the SIM card slot/3G introduces a pretty useful mod not possible on the other models (plus GPS?). To be specific, it is possible to mod the SIM slot and turn it into a MicroSD card slot with a relatively simple procedure. Such a mod allows the usage of a cartridge game and MicroSD card at the same time - other models need an SD2Vita which normally occupies the cartridge slot. However, there are some caveats to all of these benefits, as proprietary parts, “early OLED” problems, and generally clunkier ergonomics bring down the 1000 to being pretty evenly matched against it's successor.
Vita PCH-1000 "OLED" with Wi-Fi (2011-2014)
Identical to the Wi-Fi and 3G version of the OLED Vita, except there is no SIM slot on the left side, which makes the MicroSD card mod impossible, or at least extremely difficult. See above for more detail about OLED Vitas.
Vita PCH-2000 "Slim" (2013-2019)
A noteworthy update to the Vita, which improved battery life and ergonomics, changed out the charging port to be standard MicroUSB, added 1GB of internal memory, reduced weight and thickness, yet removed the 1000's forward-thinking OLED panel. Easily identified by the PS, start, and select buttons being perfectly circular. Both the PCH-2000 and PCH-1000 are quite evenly matched as devices, since the loss of the OLED in the 2000 was essentially “made up for” with the introduction of the previously mentioned general improvements found in the 2000.
PlayStation TV (2013-2016)
Differing greatly from other Vita models, the PSTV is a consolized PS Vita. Connects to DualShock 3 or 4 controllers in replacement of the normal Vita's controls. Very easily identified by it's sleek and small “flat plate” form factor that has no screen. The one obvious benefit of the PSTV is that it allows playing Vita games, homebrew, and other-such software on one's TV. In fact, homebrewing is almost a must for the PSTV, as a large amount of Vita software will refuse to work on the PSTV due to Sony-added limitations that aren't even necessary.
References
https://en.wikipedia.org/wiki/PlayStation_TV
https://en.wikipedia.org/wiki/PlayStation_Vita
https://retrogamebuyer.com/ps-vita-1000-vs-2000/
https://www.reddit.com/r/vita/comments/lw5frh/pros_cons_of_ps_vita_1000_ps_vita_2000/