Your new bike has lower gearing than your old one. This is a good example of what others were talking about with regard to gear range. The 7 speed and the 21 speed bikes have similar range. You'll have to master half step shifting to get an advantage from the 21 speed.
If you replace the cogset with one that has a twelve tooth small cog, you will regain the high gear of ~109. An 11-28 will give a higher gear. As is, you've lost some top end, but I wouldn't worry about it. 93 gear inches should be plenty. 30+ mph with fast feet.