I don't have an issue with comparing them as long as people are being consistent and objective. There are some who want to act like Jared couldn't hit the broad side of a barn, which is frankly ridiculous, and unfair to Stafford as well. The different in their arm talent isn't that wide of a gap, which makes sense, they were both #1 overall picks for a reason, they can make every throw. Stafford has a little bit more distance to his throws and throws a tighter spiral, Goff had a little bit better touch resulting in a very catchable ball. Goff could also sling it a long distance, Stafford can also add on a little touch, both could squeeze it into tight windows. People who make comments about "Oh Goff (or usually Goof, which is a bullshit name for someone who did so much for the franchise and the community) could never do that!" when we have highlights of him doing exactly that. It's silly and unwarranted IMO.
I think the biggest things that Stafford has going for him over Goff is his experience and willingness to push the ball down the field, that gunslinger mentality, as well as his ability to sense pressure and not fumble the ball, so less turnovers overall, which is huge and the reason why we traded for him. As Stafford gets more comfortable with the scheme he's only going to get better, not to look too far ahead, but I think year 2 and beyond (I assume he'll resign with us and can probably play into his 40s if he stays healthy and wants to, which if he's winning and finally playing the type of professional ball he dreamed of I think he will) he should really get better. Goff in year two of McVays system was really good, I can see that type of step up with Stafford in his second year in the system as well, but everything elevated thanks to his additional ability.
Goff's biggest strength over Stafford, at this stage, was his ability to stay even and perform pretty well in big games. Stafford just simply hasn't played in enough of them yet, so I can see why some people may be nervous when they see him a little shaky early on in some of these bigger games. I have no doubt that Stafford will perform when the time comes, he just hasn't had the opportunity to do so yet. Thus far, he's 2-0 in primetime with us, 3-0 if you count the Bucs game as a national one since it was the "game of the week" so despite some shaky play at points in the games, he's gotten the job done, which is what we needed, it's what ultimately matters.
Stafford is clearly the superior QB to Jared at this point in their careers, but Jared was good enough to win, get us into the playoffs, win playoff games, and at least bring us to the Super Bowl once. People will probably question Staffords ability to do the same (outside of winning, he can clearly do that just as well at this point) until he does the same, when you give up a winning QB who has proven he can win in the playoffs I think it's fair to make that comparison, I just don't think it's fair to use that as a reason for why the trade wasn't good or as a reason that Goff is a better QB. Goff could win, but Stafford is clearly an upgrade and anyone who thinks otherwise just isn't being honest. If you think that upgrade was worth the price or not, that obviously comes down to results, wins and losses.
If the upgrade results in more wins or losses is probably more dependent on McVay to be honest, there have been moments from him I really haven't liked. He spoke about it early on how he liked that Stafford didn't need to consult the tablet after a drive or they didn't need to get together allowing him to focus on what the defence is doing, and I really cringed when I heard that. The last few weeks I've noticed Stafford has been grabbing the tablet after drives, which is good, its what he should be doing. McVay should also be going over a few things with him if he thinks he can benefit for it. He should be talking in his ear like he was with Jared if he thinks it'll help him out. If McVay's system is really what made Goff into what he was then shouldn't it help elevate Stafford even more? Give him a longer leash for sure, but not to the point where we're taking a delay of game penalty in late in a half. And for fucks sake, enough of these "giving up" play designs on third and long.
TL;DR, Stafford and Goff comparisons are fair IMO as long as you're objective, and objectively Stafford is the better QB. It's up to McVay to make that upgrade translate to better play on the field more than anything.