It's true that larger wheels roll better on the road and they are also better for off road. A bike with 700cc wheels and fat tires (29'er) will ride through rough terrain much easier then a bike with 26 inch wheels. If you going to spend 90% of your riding on the road then 700cc wheels are also a better choice, there is a reason why racing bikes roll on 700cc wheels and not 26 inch wheels. The best thing to do would be to test ride both bikes and see which one fits and feels better to you.