one is 15hp
the other is 9.9hp (maybe)
had a 9.9 briefly. Slug. noisy. hard to pull the rope. used more fuel than I thought it should (about the same as my current 25 4 stroke). Good for a 10 or 12' boat on 10hp restricted waters. 15 destroys it in everything but weight, a 15hp 4 stroke is going to be a little heavier but it is also more power, faster, gets out of the hole better uses about 1/4 of the fuel as a 9.9 2 stroke, much much much quieter operation, more confident idle, easier to start, no smoke, no mixing oil in with the fuel, but you gotta change oil once in a while big deal.
u be the judge. Having had both I will prefer 4 stroke, even with the extra weight
the newer motors are getting better and lighter, and if you buy a new one you don't take the chance of buying someone else's problem. EFI is real nice but an old carburetor can start and run just as well if it's set up properly