I am going to buy a different boat and was wondering which motor is the best of them..I currently run an EFI on my cobra..It is the only motor I know.

Pro Xs
EFI
optimax...

Are you referring to the new ProXS or the older one? If older one, the only difference between it and the Opti, is that the Pro had a higher max RPM.

The EFI is probably the longer living motor, but get less fuel mileage.

The EFI is historically going to live longer. Just the nature of more fuel/oil running through the motor keeping it lubed and cooler. The other two are just optimax and optimax with stickers.

You'll need to weigh durability vs fuel use.

Pat The older ones.. I hear the optimax seem to blow more engines that he EFI.. Is that true?

the older the optimaxes are the more prone they are to failure.

Yes...and no.
They were called opti-pops for a reason. All of the DFI motors were fragile when they hit the market, if you had a diligent owner who kept up with the updates and maintenance, they do live longer, but personally, I wouldn't trust them.

Any 4 stroke!
If 2 stroke, I’d go with the V Max

This, ran mercs nealy my entire life of six decades. I just bought a Skeeter with a 200 SHO 4 stroke. I run it quite a bit when I'm on the water and about every two or three trips I add $50 of fuel spilttling it between two 25 gallon tanks that were close to empty when I got the boat. I've had the boat about six months and have about 2/3 of a tank in each of them, slowly gaining ground. I'll probably run it for a while without adding any fuel because I don't want the weight of full or nealy full tanks to push around. I run no ethanol fuel as well and it seems to like that.