When two boats share the same hull type — in this case both the Shallow Sport 20 ft. Classic 2011 and the Shallow Sport 21 ft. Sport 2011 are tunnel designs with composite 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?
Both boats share a closely matched power ceiling — 200 hp for the Shallow Sport 20 ft. Classic 2011 and 200 hp for the Shallow Sport 21 ft. Sport 2011. Real-world performance will come down more to which motor is actually bolted on, its load at the time, and whether it's a 4-stroke or 2-stroke setup. Both carry nearly identical fuel loads — 43 gal and 43 gal — so range won't be a tiebreaker here.
For family outings this is probably the sharpest distinction between the two. The Shallow Sport 21 ft. Sport 2011 is rated for 7 passengers, while the Shallow Sport 20 ft. Classic 2011 caps at 6. If you're regularly pulling extended family or a group of friends onto the water, the extra seats on the Shallow Sport 21 ft. Sport 2011 could be the deciding factor.
Bottom line: Choose the Shallow Sport 21 ft. Sport 2011 if your priority is putting more people on the water — it handles 7 passengers and at 21,0 ft it has the deck room to back that rating up comfortably. The Shallow Sport 20 ft. Classic 2011 is the smarter pick if you want a lighter, easier-to-trailer boat rated for 6 that costs less to run day-to-day.