All good input but perhaps the biggest factor is how much you know about bicycles in general as they do require maintainenence. That plus the added complexity of the assist system of your choice means if you are not mechanically inclined you will be best off seeking a source for you ebike from someone that is close by that has knowledge that they can share and even if their product is not the absolute best in the market the fact that they know it and have the parts and ability to help you out when and if a problem occurs so that you don't have to go to the internets for advice all the time you will be better off in the long run.

That said a five mile commute even in hilly terrain should be well within range of just about any ebike out there. If you are unsure about the whole thing perhaps the best thing to do would be to get a cheap one to start out and work your way up from there as necessary. Good luck and you have the right idea, stick with it. And don't forget to pedal!