Primers work, but it is way too easy to flood an engine with it. I know cuz I did it lots of times. Chokes are more fool proof.
Shut-offs are a must and are recommended by all manufacturers if you "trailer" the sled. Trailering vibrates the heck out of the float valve and will put raw gas into the engine. Yet another reason to have EFI since they won't be doing that. Lots of sleds have burned down at the first pull after a trailer ride.
As far as a primer is concerned you don't have to drill the carb out. Just put a "bleeder hose in the intake of the carb. Priming puts a shot of fuel in the carb to draft into the engine without need to have fuel all thru the system which is what a choke does. Newer sleds should not need them, unless you get one with a primer. Besides a primer needs to be pumped before starting and then a few times after it starts to keep it running. They work best in very cold climes.
Don't need to do all that with a efi system since once primes the pump and the second pull will fire it up.