Well, I have no racing background or particular type-A drive to maximize windward performance, so take my comments with that in mind. Here's a few thoughts on the spritsail vs. lugsail experiences I've had:
1. The lug rig can be dropped instantly because the weight of the yard drops it right down, and the sail isn't attached to the mast so can't bind. The spritsails I've used didn't even use halyards, so you either had to brail them (leaving lots of windage aloft) or pull the entire mast out to drop the rig.
2. Reefing--already mentioned, but lugsails excel at easy fast reefing. That can keep you comfortable sailing as it breezes up, nice and in control. Spritsail reefing systems tend to be much more complicated.
3. I found sometimes that it was fiddly trying to keep the sprit in the peak grommet when trying to hoist the spritsail. This can probably be solved with some kind of rigging trick, but the lugsail has no such complication.
4. A balance lug rig is self-vanging to some degree, and is very gentle in a gybe because the sail area forward of the mast opposes the sail area behind the mast.
Upwind, I've never had any trouble with the 76 sq ft balance lug rig. In the 2016 Texas 200, there was one leg with about 6-7 miles dead to windward in a narrow channel. Many boats motored, or quit, or took a tow. My friend and I just tacked casually upwind the whole way. I think the Phoenix III is a very good windward boat, even with the lug rig. It tacks very quickly, loses little momentum, and keeps good speed to windward (by casual comparisons with my new boat,
an 18' lug-rigged whitehall designed by Don Kurylko, the Phoenix III is always faster to windward, by quite a bit).
Both rigs do well, though. Spritsails were the dominant traditional rig on the east coast of the U.S., whereas lugsails never caught on there. Both set on an unstayed mast, which will keep rigging fast and simple. I just find that there's less fussing and complication with a lugsail. If you're more performance oriented, you'd probably be interested in Michael Storer's archive of lugsail tuning and rigging:
https://www.storerboatplans.com/cate...lug-rig-setup/
Tom