Both the Go-Devil 18 x 38 2011 and the Go-Devil 20 x 48 SD 2013 are flat-bottom designs, both built in aluminium, so 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?
On paper these two are close siblings in the size department - Go-Devil 18 x 38 2011 at 18,0 ft versus Go-Devil 20 x 48 SD 2013 at 20,0 ft. Weight tells a clearer story for trailering families: the Go-Devil 20 x 48 SD 2013 tips the scales at 590 lbs - 160 lbs less than the Go-Devil 18 x 38 2011 at 430 lbs. That difference is meaningful if you're working within a half-ton or three-quarter-ton truck's tow rating, especially once you factor in a motor, gear, and fuel.
Both boats share a closely matched power ceiling - 30 hp for the Go-Devil 18 x 38 2011 and 40 hp for the Go-Devil 20 x 48 SD 2013. 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.
For family outings this is probably the sharpest distinction between the two. The Go-Devil 20 x 48 SD 2013 is rated for 6 passengers, while the Go-Devil 18 x 38 2011 caps at 5. If you're regularly pulling extended family or a group of friends onto the water, the extra seats on the Go-Devil 20 x 48 SD 2013 could be the deciding factor.
Bottom line: Choose the Go-Devil 20 x 48 SD 2013 if your priority is putting more people on the water - it handles 6 passengers and at 20,0 ft it has the deck room to back that rating up comfortably. The Go-Devil 18 x 38 2011 is the smarter pick if you want a lighter, easier-to-trailer boat rated for 5 that costs less to run day-to-day.