I've been out of the loop for over 7 years so I could use some help. Looking to get my next one with mild power (496HO, 500EFI, 575SCI) and have the list narrowed down to:
Formula 353 Fastech
Hustler 344 Cheetah
Sunsation 32 SS/Dominator
Nordic 35 Flame
Fountain 35 Lightning twin step (staggered or side-by-side engines)

Pros/cons of each model? I'm leaning towards the last two and away from 525EFI due to topends/headers. Will be used on a couple calm lakes with an occasional trip to LOTO. Any advice is appreciated.

Formula probably rides the best and has the best build quality. I loved my 330. I’ve never been on the other boats. Hustler and fountain would be fastest.

Following...

Disagree. Assuming equal power, the Sunsation will be a faster boat than the 35 Fountain. Especially if it's the newer twin step SS/SSR/XRT bottom.
Source: Used to own one, and spent a lot of time on the other.

I ride very often in a 2008 Sunsation 32 with whipple charged 500 EFI's. It runs and handles great, also would be my next choice if I didn't have my 33 Active Thunder. I have rode in a newer staggered 35 fountain as well as a 344 Hustler, both with 525's. I liked the ride of the hustler compared to the Fountain or Sunsation. For all around looks and feel of everything I like the Sunsation. All 3 three are great boats and each person will have their own opinion on each. I would not stray away from the 525's. Each of the engines except for the 496's will need top ends around the same time as the 525's. The closed loop cooling in the 525's is a plus. As far as headers go most have been fixed or changed out to Stainless Marine exhaust. The 496's will last forever, but they don't have the performance and sound like the others listed. I can't comment on the Formula or the Nordic since I have no experience in either of them. Do your homework and try to get a ride in each of your choices to help with the decision.

I had a 35 Nordic for 3 or 4 seasons. It was a nice boat. Ran good, handled good. It ran mid 90's. Build quality was OK, certainly way better than a Fountain, probably about the same as a Sunsation, nowhere near as nice as Formula's build quality. I am not familiar enough with the Hustler to comment on them. 525's would be my FIRST choice of engines. Pretty good performance and limitless possibilities with them. I personally really like the 575's, but you need to be a mechanic to own them. With a few upgrades, they are a reliable 700hp

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Sunation is the fastest out of the boats listed, Tallest cabin , Lightest boat of the bunch so you give up a little ride quailty until you learn how to drive it, Most updated of the bunch. Seems like the Fountains are now showing signs of rot, I took a owner of a flame a ride on mine and he said it rode better and had more room so he ended up buying a 32. I have been told the Cheetah rides like a bass boat.

I know you stated stepped, but in your backyard depending where you are in Central, IL (I'm in Bloomington so this is 15 minutes from me).

https://www.offshoreonly.com/classif...ob-o81776.html

Have a lot of time in a couple of these on LOTO. Other than lacking freeboard of the SS/SSR/XRT/Innovator, cockpit is identical. Nothing wrong with the vented chine/pad of these in terms of ride quality in the rough and this is a legit 80 MPH boat with HO power. You'll appreciate the forward seating if you have more than 4 on the boat at any time.

Scarab 33AVS could be a good one to consider too.

A 32' Sunsation with the same power as a 35' Fountain with stagged engines is faster than the Fountain? No way