RE: Replacing a 105L Hyper
I feel a bit sheepish because I'm not experienced with any of the specific boards you are debating, but forgive me that and just consider theory of board quivers. I live in upstate NY, so am at least familiar with your conditions, and sail a LOT on Lake Ontario and the St. Lawrence Seaway.
Inland great lake sailors are predominantly frontal sailors, with maybe a touch of summer afternoon thermals 1 day in 10. Well, the thermals work more than 1 in 10, but they only make the difference for a windsurfer 1 in 10. Moreover, you're talking fresh water and the boards are built / sized for marine conditions (salt water).
THEREFORE: the vast majority of days will be light to moderate and, given that, anyone who's top of a two-board quiver is designed for anything but 6.0 - 8.0, has made a BIG mistake. The lower your biggest sail is, the MORE LIKELY you are to be sub-planing. Now, I'm no fan of formula or free-formula stuff, but I think you want a board that will do well in marginal to good 8.0 conditions.
Your second board must complement the first. In Lake Ontario, that is going to mean pretty good size swells any time the wind is bigger than 6.0 conditions. So I would probably pick a second board designed for moderate to big, to VERY big swells in the 4.0 - 6.0 range. In fresh water, I think 74 may be a tad small for that, especially in a full 5/4 or dry suit (as it is most likely to be that windy in cold weather / water), but it depends on your efficiency and true weight, the local break, etc. Not having sailed it, but having sailed a sister board, I almost certainly would recommend the Kombat 79 as this board (at your weight I think it'll be a 4.0 to 6.0 board...you probably will be able to squeeze it to 3.5). I don't have an Acid, but I have a similar board and I think it'll leave you with a gap if you size your moderate wind board correctly. A slightly bigger Acid would probably work, but I think a Kombat will be more versatile.
In sum, the problem with inland great lakes sailing is that it's kind-of difficult to do it in a 2-board quiver. It really needs 3 - a 120L+ size, a ~100 L size, and a ~75L size (or smaller). If you really must do two, I'd recommend 100-110L SLALOM style board, and ~80L WAVE / CROSSOVER board.