My own thinking is that 3.7 degrees is wide enough. When you start going to shorter focal lengths field curvature becomes an issue. With my 80 mm F/6, despite a nearly perfect eyepiece like the 31 mm Nagler, the scope's field curvature mean the outer field is not so pretty.
I think Alan summed it up and myself, knowing what I know having owned these scopes, I'd go with the AT-102ED.
I'd say 3.7 degrees very likely is enough. And yet you once chided me for never knowing the true joy of wide field viewing because I'm "stuck" with these 4.5 degree 92mm options (Stowaway and CFF). The gist of the comment was that f/5.5 and a 31mm Nagler was transcendent and f/6.6 and XW40 (4.5 degrees) is mere piker.
But perhaps you were annoyed with me that day. It has been said, that I can be annoying.
Notwithstanding: 3.7 degrees is in the territory of the max FOV of a GT130 (3.4 degrees). It is to be noted that 3.4 degrees is not really a narrow field view, and that part of these considerations is how much aperture is delivering the field. A 5 inch 3.4 degree fov is very different from a 3.6 inch 4.5 degree FOV.
Since it is OP's first refractor I would be inclined to recommend the 4 inch so he can see what it is all about. Plus it puts him squarely into the territory that is covered by Sky Atlas 2000 or Skiff-Tirion's Bright Star Atlas or Sue French's Sampler book and articles.
I thought the f/8.1 Tak FS128 was a very capable "wide field" scope even though its max was 2.7 degrees. But using an SCT will do that to you: make you think 2.7 degrees is a nice wide field. The Tak with a 40mm XW offered the same FOV as the GT130 with a 30mm XW. In terms of my personal viewing habits, f/7 would probably be a better spot for me than f/6.3. But f/6.3 isn't shabby.
Coming back to OP again: I'm not sure why we are worrying about chromatic aberration on the moon or Jupiter. If it is a good ED it won't have any in focus. If it's not a good ED, well then, don't get it. What's the point of paying for color control if you don't get color control. But it is true that variation among ED options is one of the things to be careful about when buying.
Edited by gnowellsct, 16 October 2020 - 01:01 PM.