Before winter, I'll be replacing two furnaces in park owned homes. Currently all units in the park are propane. This is (cold) midwest rural area but with fairly reliable electrical service (knock on wood) - we're two miles from the substation and I don't think there's even a tree between here and there to fall on a line.
Propane advantages: Some security for me knowing if we had a power outage, they would still have heat and I wouldn't have frozen pipes, although most is pex that's been insulated and heat taped.
Electric advantages: This appears to be a tenant preference, I assume because they pay for it monthly and don't have a large bill at irregular intervals the way they might with propane. In my experience it's more likely a tenant will not be able to fill up their propane tank than it is that we'll have an extended power outage. The propane company has been nothing but problems for me in the POHs and at the park in general and I'd love to free myself of them.
I haven't looked at cost or efficiency of propane vs. electrical yet. I've always thought that it was safer for them to be on propane because of the rural location but if the tenants prefer electrical...