My personal experience....
Test boat. 2012 war eagle 548LDV. W45 trolling motor on port side of bow. Low deck. Single battery in the back. Tackle box usually in the middle somewhere and a cooler directly in front of the rear seat, usually holding a 10 lb anchor and some rope. At time of testing, no fish or ice were in the cooler. Just me in the boat and I'm 200 lbs. Hull weight 341 lbs + trolling motor, battery, wiring, 2 running lights and gear.
Motor was a 2007 Yamaha 25hp 2 stroke, twin carb. Bone stock. I had bought it with intentions of reselling it. Motor weighed 114 lbs (electric start short shaft manual tilt tiller steer) on my scale. Mounted to the transom with exactly 2" of lift between the motor and transom top. Top speed 28.6 mph is the highest sustained speed I found with the GPS, at 6070 rpm. ~700 RPM idle speed to plane 3.5 seconds. Minimum planing speed 12.9 mph at 4200 RPM. Prop was 9 7/8" diameter, 11 1/4" pitch-brand new OE Yamaha replacement white aluminum 3 blade.
Loaded, drove home (about 2 miles) and pulled the 2 stroke off the boat, and bolted my 4 stroke in the exact same place. 2000 Yamaha 25hp 4 stroke. Weight 138 lbs. Electric start manual tilt short shaft tiller steer. Drove back to the lake, within an hour of the 2 stroke run.
Top sustained speed 28.9 mph at 6110 rpm. 740 RPM idle to planing speed 3.4 seconds. Minimum planing speed right at 13.2 mph at 4210 RPM. The prop was the exact same prop that came off of the 2 stroker. AL 3 x 9 7/8" x 11 1/4". I just pulled the prop off and stuck it on the 4 stroke just to keep everything about equal, to satisfy my own curiousity. I can get out of the hole a lot quicker with a 10" on the 4 stroke but then it is on the rev limiter at 26.5 mph.
Best I could tell, there wasn't much difference other than the 4 stroke didn't smoke. And it's easier to start, IMO (no choke).
I can't speak for other manufacturers of boats or motors since that's the only real testing I've done to speak of. Have run lots of flat bottom tins with lots of different motors but never put a pen to paper and actually tested those others, only my own. I did do some testing on a 15hp Yamaha 4 stroke on the same war eagle boat and it was a slug to get on plane but still ran 24 mph, which impressed me.
25hp is 25hp, in my opinion. Some manufacturers pay little attention to satisfying the older crowd and just build a good 25, but it may be down on torque or down on HP compared to the same 2 stroke horsepower. Having spoken with engineers for Yamaha, they wanted to try as best they could to keep the 2 stroke and 4 stroke about the same in power and torque output.