I recently rode the city commuter with 28" wheels. I am only 5'7, and found the size to my liking. The smaller wheels would be more agile for fast turns, etc.. but I assume you aren't planning on hardcore mountain biking. Go with the bigger wheels.
The frame size is far more important than wheel size. I have 700c, 26 inch and 29 inch wheel size bikes. The frames are all different as well, because the frames are designed for different things.
Generally speaking larger wheels will give a longer wheelbase and more ground clearence. Neither wheel size fits a taller, longer inseam person better than a shorter person. I've known shorter riders to ride 29'ers, but with 16 inch frames.
Frame size determines whether a bike fits or not. It's possible to make an educated guess, but with ebikes, that could be an expensive mistake. If you don't know the best size bike, it's best to get a professional fitting and do test rides. Your local ebike shop may be able to do it, if not Google bike fitters near you. Everyone has access to a good bike fitter these days. I've seen fitters charge $60 and up. They generally have reviews online.
Concur with the others that frame size is the important thing for bike fit and wheel size is for intended application (either wheel size will work for you as long as the frame is a good fit). In my regular bikes, I have a trekking version of the Tern folders with 24" wheels. It is agile, corners well and quick to get going from a stop. Then I have my Spot with 28" wheels. It puts you higher up and is fast and smooth over long open distances. So I think the wheel size is more about what type of riding you will do and is really independent of frame size (smaller wheels also make it easier to pick up and carry or throw in the back of a vehicle).
Wow, what a difference trying out the different size bikes makes... Wife and I (she's 5' 4") are both going with the 28" inch City Commuter Step-Thru Bikes 14V 15ah... 26" was slower and felt like a toy compared to the 28" which was zippy and felt more like an old 10 speed from the old days. Thanks for all your feedback!