Actually, once you git'r going, you can't tell the difference. My daughter's bike has a 350w front hub and she and the wife love it. Top speed is around 18 mph. It's a small motor so acceleration needs some pedal help.
My bike has a 450w gear drive motor on the rear wheel and is "external", having to be mounted to the frame and is chain drive. Top speed is 20 mph with some pedaling to get there. Wife likes this one too, but likes the "stealth" of the hub motor. Btw, I'm pushing 220 lbs., so I'm getting pretty good performance, considering.
Both are 24V and uses 2 12V SLA batteries in the pack. They're okay for short commutes which would be under 10 miles, but I wouldn't push it past 8 and that's still with some moderate pedaling. Better still if you can charge your battery at work or can carry a spare pack. My commute is only 2 miles one way, but there's a pretty good hill I have to ride and is longer on the way home. I still throw the battery on a charger at work, just to make sure I have the juice to help my up the longer hill. The weight of one pack is bad enough, two would be rediculous on my bike.
If your commute is longer, go with what Deacon said about the 36V units and possibly a trailer to haul a spare batter pack or even the whole drive unit.
I've recently been looking for a single child bike trailer to haul an extra pack and for the extra storage. We can find them around here on CL or garage sales for fairly cheap.
As an option, you can check out Currie Industries at
https://www.ezipusa.com/159-currie-electro-drive-conversion-kit-w-plug-play-battery-pack.html
Their new kit is what I have, less the fancy batt pack and rack.