Hey man, snowshoe sizing like boards are based on weight.
Rule of thumb is the larger the snowshoe the more float you will have. You need to consider how much you will weigh loaded with gear. Also, if you are going to use them for daytrip stuff or maybe an overnight trip. You are obviously going to be carrying a lot more weight if you are going on a hut trip.
I would say if weight wise you are at the upper end of a snowshoe size, go the next bigger. If your snow is more of a continental snowpack a larger size is a good idea too. Snow in continental climates is notorious for low stability underfoot. So a larger surface really helps. If you have a maritime snow pack, that snow tends to consolidate well and support, so less of an issue.
Better yet, get a splitboard...