Ive had both the Strida3 and Strida5. I first bought the 3 and liked it, but I was leery of the plastic BB and wheels. I'm 6' and 190lbs. When the 5 came along, I thought it was overpriced at US$800. When I found it for $600, I jumped at it. (I probably would not have bought at $800.)

The 5 is definitely a nicer bike. In addition to the obvious changes to the wheels, brakes, BB and crank, there have been many little, subtle things improved. They clearly incorporated a lot of user feedback in the design of the 5. I feel very confident on it.

So, my bottom line is if you're a genteel, occasional rider, then the 3 will be fine. If you're going to ride a lot and ride seriously, the 5 is worth a couple hundred more.