I know someone who swears by her model 28, gives perfect stitches and all over a very smooth machine. It's like she has an extra well made 28 or something. I don't know shuttle machines that well and should probably not argue for either of them. Personally I lean towards model 66 with the round bobbin, it's a very solid, smooth running machine and a joy to work on. It's easy to get bobbins for it, but from the right source, there's plenty of new bobbins for the 127 too. If the price isn't very off, and assuming both are intact, I might go for the machine in the best cosmetic condition. I assume you will have to do a lot of cleaning and oiling regardless of choice, but that's half the fun ;- )
I don't know what you mean by high position near wheel, but I assume they both are or will go in a treadle cabinet, and it's between a model 127 and a model 66?