Re: Weaver Tactical GS vs SWFA 10x42M for Rimfire
The only restrictive factor with the SS is its fixed power. If you have no problem using 10x at all ranges you'll be shooting (whether its 10yds or 250yds), then the SS is the better option of the 2 scopes based on several factors, but mostly on its HUGE adjustment range compared to the Weaver (the SS has basically 2x the internal adjustment range of the Weaver which you'll find extremely nice...and necessary...for a long-range 22lr trainer).
The variable power really only shines when it comes into needing less magnification and a wider field of view that comes with it (like when hunting for example). For 50yd work (your stated shortest range)...the fixed 10x should be fine.
Just to add one other thought...if this is truly a "trainer" in the strictest sense of the word, my advice to you is to buy a scope that mirrors the scope that you'll be using on your centerfire counterpart to your .22lr trainer. I know people don't want to spend that kind of money sometimes (especially when its the cost of a NF, USO, Premier, S&B, Henny, etc.), but if you are truly "training" then it makes sense to have your setups as close as possible to each other in terms of function if nothing else.