Yes, to my mind the marriage extension will always have more weight than a retirement extension, and that is one example. Also there was a period I think (and I'm a bit hazy on this) that visas from abroad and /or re-entry permits based on marriage required just Covid insurance, but the retirement ones required that plus the 400/40 k (for the COE) ?
Anyway I am married but went for the retirement extension due to the reduced documentation and the fact that there is no under consideration period, and to do away with the hassle of home visits, witnesses etc
Also for the original poster - I don't believe that changing to a retirement extension is a one-way trip. I think you can change back to a marriage extension at a subsequent renewal anniversary if that is advantageous to you. The IO may not like it as it is extra work, but I think it is permitted. So if that is the case, there seems to be nothing to lose.