I would not go with a pre-3 Geo, so given that I would recommend the Etek 5 out of those two. But if you can snag a 3.1 within your budget, that's a great route. Obvoiusly, preference is big here--do you prefer spools or poppets? The Etek 5 is a very nice shooter and feels great in the hands but the 3+ Geos are fantastic, as well.
This is a geo 3 bolt
This is a geo 2 bolt
They look the same to me. I know for sure that the geo 3 and 2.1 use the same regulator and ASA, same gripframe and grips. I believe the only differences between the geo 2.1 and 3 are milling, eye covers, and the allen key adjustable solenoid. I myself have owned a Geo 2 in the past and it is a good marker. However I would not get a geo 1 or geo +. But the geo 2.1 is definitely a good option.
Edit: Geo 3 has a soft tip bolt, but an upgradable soft tip is available for the 2.1
They may look similar but that doesnt mean a whole lot. Due to the Geo 3's solenoid it can get significantly better efficiency (I believe Eclipse calls it the ICSIS valve or something like that).
The Geo 2/2.1 is still great, but 3s barely $100 more now so unless youre on a tight budget its worth it to get a 3 IMO.