The Umarex Gauntlet is the better rig over all. If your old or such the weight may be a bit much with the guantlet otherwise it is THE value in pre-charged airguns these days.
Out of the box, adjust trigger then enjoy, period. I have a .177 that would do well at any airgun match. Friend has a .22 not exactly as accurate ( but he insists on the cheapest pellets) but would never miss a squirrel head at 50yards. They need nothing done to them - other than adjust trigger-.
Gamo darn sure is lighter, trigger isnt as good but works just fine people do sell after market kits and most just use a longer screw for additional adjustment range, needs a 3,600psi fill and will have a limited shot count but it's a small tube so easy to pump.
Depends on your shooting desires a lot also.
Do you want 10 reasonably good shots on a fill or 50-100 shots within 10fps? Are you physically fit? Are you a trigger snob?
Here's one that doesnt matter, are you able to cut & crown the guantlet? I saw a picture of a carbine gauntlet, very nice!
Mainly,
Have you gotten together with other airgun folks? Tried what rigs? And liked/disliked what about those? Esp. for a first ( and last right?) rig shooting first is a very good idea, well worth a fairly long drive in my mind. Airgunners are usually pretty open about letting others shoot there stuff and you'll learn a lot. Anyone near 99109 can stop by here and shoot.
John