When two boats share the same hull type — in this case both the ThunderJet Alexis OB Offshore - 21 ft. 2008 and the ThunderJet Maxim - 25 ft. 2008 are modified vee designs with aluminum construction — the buying decision usually comes down to a handful of practical questions: how many people are you putting on the water, how far do you trailer, and what does your tow vehicle weigh?
The power gap is worth calling out. Rated to 525 hp, the ThunderJet Maxim - 25 ft. 2008 has a 25-hp advantage over the ThunderJet Alexis OB Offshore - 21 ft. 2008's 500-hp ceiling — enough to notice on acceleration and at cruising speed, particularly with a full passenger load. Fuel capacity breaks the other way: the ThunderJet Maxim - 25 ft. 2008 carries 11 gallons versus 5 gallons in the ThunderJet Alexis OB Offshore - 21 ft. 2008. On a lake day that's negligible, but for coastal cruising or long reservoir runs the extra range matters.
For family outings this is probably the sharpest distinction between the two. The ThunderJet Maxim - 25 ft. 2008 is rated for 10 passengers, while the ThunderJet Alexis OB Offshore - 21 ft. 2008 caps at 6. If you're regularly pulling extended family or a group of friends onto the water, the extra seats on the ThunderJet Maxim - 25 ft. 2008 could be the deciding factor.
Bottom line: Choose the ThunderJet Maxim - 25 ft. 2008 if your priority is putting more people on the water — it handles 10 passengers and at 25,0 ft it has the deck room to back that rating up comfortably. The ThunderJet Alexis OB Offshore - 21 ft. 2008 is the smarter pick if you want a lighter, easier-to-trailer boat rated for 6 that costs less to run day-to-day.