Thanks for the replies so far.
The 34 will be my competition gun (Idpa)
I have a few CCWs already so I probably won't be carrying whichever one I get. I'm kinda leaning towards the 17, but then again if I'm getting the 34 anyways it might be better to get a compact like the 19.
By the time I change out the ejector/extractor and the barrel I could just buy another used one. Somebody had told me all I needed was the barrel (and mag of course)
Keep the responses coming!
The G17 uses the same magazines as the G34.
The G19 can also use the magazines of the G17/G34 but they protrude slightly from the grip.
The G34 and the G17 are identical except for the competition parts and the longer barrel/slide. All their parts will interchange.
To echo Tailgator, you should check the fit to your hand. The G19 fits my hand better than the G17/34. The grip hump sticks out below my palm slightly on the G34/17 and it isn't as comfortable to me as the smaller frame.
You can usually get a G22 to fire with a 9mm barrel but it might not be reliable.