By "with a throttle", are you looking for an ebike classified as a bicycle (up to 20mph) that can go on bike trails, etc., or a higher speed pedelec?
As for most reliable... there aren't any comparative studies of ebike reliability. I went with Pedego, which has a shop near me as well as a 2 year parts and labor warranty. If reliability is important to you, I suggest you get a bike that will be supported by a local bike shop near you. Then, when there is a problem, they can fix it and may even provide you with a loaner if they have to wait for parts. Be sure to ask any shop about service-related policies, etc.
I'm sure others will chime in about their own experience with their ebikes.