Experience so far: gas bike and ebike
Gas bike is Straton friction drive, Subaru/Robin 33.5cc 4 cycle on a Trek 920 mtn bike. Miles to date are 200, mpg avg is 114, trouble is none. Starting is almost always first pull.
Cruise speed is about 16 to 18 mph and is very smooth. Minimum speed is about 12 mph for clutch hookup and vibration starts at about 20 mph. Range is 12 to 18 miles before running out of gas. Top speed is I don't care.
The gas bike is much lighter than the ebike, that matters when parking but not much when riding. In a few seconds the roller can be raised off the tire for drag free pedaling.
Noise is apparent to the rider, especially clutch ringing clatter but pedestrians don't notice the motor very often. I wear earplugs for the noise.
Throttle is a pull trigger, it is very comfortable and nice. Tire wear is negligible.
Acceleration from a stop is done using the front middle ring and heavy pedaling, along with some throttle and clutch slip. Cruise is done using the front big ring and some pedaling. I never shift on the rear cogs, unless using pedal power only.
The ebike uses an Aotema direct drive brushless front hub, it weighs about 15 lb. Batteries are 3x 12v, 12ah, SLA, the pack weighs 25 lb and sits on the rear rack. A thumb throttle is used and it is painful to use after the first mile. Bike is a classic mountain bike. The handlebars need more rear sweep, the throttle needs to be a twist grip.
Cruise speed is in the 8 to 14 mph range. Min cruise speed is about 4 mph because of cogging, top speed is unknown. Total miles are 40, most rides are 4 to 5 miles but a 14 mile ride was easily within the bikes range. Avg speed is about 10.5 mph and average power is about 185 watts, using about 5 amps average. Pedaling without power is not fun because of the direct drive hubs drag when not powered.
Acceleration away from a stop is an ebike strong point, just give it some forward motion, add throttle and pedal some. The front stays on the big ring, the back cogs are not shifted. I tend to pedal less on the ebike than the gas bike. Stop signs are much easier on the electric bike.
The front hub motor, controller and battery pack add about 45 lbs to the bike. Parking can be a hassle but the weight is not felt much when riding. I do feel the mass of the front hub sometimes.
Noise is hardly noticeable. There is some hub ringing below about 10 mph but pedestrians probably do not notice the bike is powered. I don't wear earplugs when riding the ebike.
Mounting and dismounting the battery pack isn't much hassle but I can just pull and go with the gas bike.
For comparison, my scooter has a 163cc gas motor and CVT transmission. It is a miracle of smoothness and comfort compared to the powered bikes. It averages 65 mpg and can cruise at 55 mph, though 45 is more fun.
Thoughts: a Golden Eagle belt drive would probably give higher mpg than the Straton friction drive but the FD is just so easy and trouble free and easy to deal with after running out of gas, that I'll stick with it.
Gas or electric? Get both is the only reasonable solution.
Hope this info is useful to someone.