Ok, I wasn't going to weigh into a "what's best" debate but I do have an old type eleven 5 1/2 inherited from my dad. It has become my absolute favourite bench plane & gets used daily. I like it because of the lighter casting - at my age, pushing extra metal around for no good reason is not as much fun as it once was (I have a very nice skewed-blade infill panel plane, but it only gets used for fine finishings due to its heft!).
The problem of replacing blades in the 2 1/4 inch jobs is much exaggerated, imo. I bought a new blade for mine in complete ignorance of the size issue, which I only discovered when I went to fit it. Had I done some very simple research beforehand, I would have known & maybe wasted much time & energy looking for the 'right' blade. The blade I bought (Veritas), was certainly a bit wide & would not fit initially, but it didn't need much ground off the sides to get it to fit, certainly not a full 1/16" per side. Stanley wasn't all that fussy with mouths and there is a good deal of room on most old planes I've had much to do with, anything from 1.5 to 2mm. I doubt I removed more than .5mm each side.
Having the mouth just wide enough to admit the blade is a good thing, imo, because the blade pivots on the edges of the mouth and it makes lateral adjustment more consistent & repeatable. In fact, my Norris A5 has a convex disc either side of the mouth that can only be there for that purpose, as far as I can tell.
Whatever, I sure wouldn't worry too much about having to replace a blade in a 2 1/4" model of the 5 1/2 (pre-1935, iirc), they may not all be as easy as mine turned out to be but if you have access to a grinder it shouldn't take you too long to have it in place. I made a crude jig to keep the sides straight, & snoothed them with a diamond file once the bulk removal was done (new blades are hard for their full length, & I couldn't cut the upper end with a regular file).
Cheers,
Ian