I've put close to 13K miles on a Stromer ST-1; it's worked so well I got rid of my car a couple of years back. My current commute is 13m each way, and involves a fair stretch of MUP (the Mary Carter Greenway trail) so I limit my speed more than a little. Pick the bike that you are most comfortable on, in the long run that is (IMNSHO) the strongest factor governing how much you'll end up riding ;>