I think the higher you go, everything improves. I know many people had problems with their GX getting ruined too quickly. The others should last a really long time.
Of the three I would recommend the Line6 Pod Studio UX2. I bought the UX1 and regretted it luckly was able to return it and buy the UX2. The GX is the worst though.
The GX just has an input for guitar and one for headphones.
The UX1: has input for guitar, an input for mics so if you want to mic an amp or do vocals someday. 2 line inputs so you could also record keyboard and line instruments. A stereo input to hear music without it being recorded. A headphone input to use headphones and 2 analog outs to connect to speakers. That is so much more than the GX.
(GX and UX1, you could only record one instrument at a time)
(with both the GX and UX1 you might experience the sound clipping if the signal is too strong)
The UX2: 2 inputs for guitar. a headphone input. 2 mic inputs which is useful if you ever want to mic something. you could use two mics at once. also has a button for phantom power to allow you to use condenser mics. (the UX1 does not let you use condenser mics). UX2 has 2 line inputs to record keyboard and line instruments. 2 analog outs for connecting to speakers, stereo input just like the UX1. digital out. (not sure what it is) 2 footswitches inputs. so you can connect footswitches to it and send midi signals. for example: in pod farm you can save a set of gear lined up and play through it and set the foot switch to change between different gears ( clean to distortion) (like channels on an amp) ( i haven't tried this out yet but will sometime soon).
The GX comes with Pod Farm regular version, Ableton Live Lite 8-track (you only have 8 tracks to record- for ex: guitar, drums, piano, etc) also comes with riffworks. small version. Does not save just loops and for jamming.
The UX1: comes with Pod Farm regular version: (plus you get a bonus of 35 effects and stompboxes= much more variety. worth the extra money) Ableton live lite 8-track. Riffowrks small version.
The UX2: Comes with Pod Farm regular verison (plus you get a bonus of 35 effects and stompboxes= more variety) Ableton live lite 16-track (way more than the other two. you'll probably never need 16 tracks but you might want more than 8 one day. It also comes with Riffworks small version. and Reason Adapted which is a virtual studio with all the mixers. You get to create drum beats with it. ( also with ableton) reason also has syths.
I wouldn't recommend the GX at all.
I would recommend the UX2 because for the small money difference between it and the UX1 you get soo much more. 16 tracks to mix. reason adapted. and also gives you the extra effects for pod farm (so does the UX1). you also get to use footswitches so you could use pod farm like an amp and make up your own channels and stuff. phantom power. you'll be safe in the future.
I would also recommend you get some good speakers to use. It'll sound so much better. Don't use your amp as a speaker. it could mess it up and the sound will be different that you hear through your amp then after you record it and listen to it in your car or somewhere else. If you use your guitar amp you'll hear to sounds at times- the sound of pod farm and the amp- so it'll be like an echo.
If you need help choosing good speakers, let me know.
I would hightly reccommend the UX2. You can't go wrong. GX= wrong. UX1=good choice but might regret it in the future. UX2= perfect choice.
by the way. the UX2 lets you record two instruments at the same time. the Pad input gets rid of clipping if your experiencing it with the other input. good to have.
Right now at guitarcenter they have the Pod Studio UX2 for 159.99. (10 dollars more than the UX1 at regular price) They have it that price this month. You should get it before it goes back up to 199.99.
I hope this helped.
If you have any questions you can send me a message and I'll try to help you out, weather its about this recording stuff or just guitars, amps, music theory, anything about music.