Are the mecanum wheels considerible faster than the 6 wheel set up that came with the kit?
There are a lot of variables that affect this question–gearing, motors, and wheel size. Without more information, I’d say that 6 wheel drive robots are generally faster. However, that might have more to do with the difficulties teams have in designing mechanum systems.
With the three years on my team I experienced the use of two rear wheel drive with the front being casters(2007), mecanum wheels(2008), and two rear with the front solid wheels(2009). Each of those systems had their positives and negatives for those games.
Speed wise there are multiple variables that can come into play like mentioned above and it matters on how you set everything up. But too you want to think of other features of your robot and what the benefits and negatives to using a certain drive train. Like controls, movement( do you really need sideways movement or can you survive with just turning), and other things you can think of.
One thing I slightly remember when we used mecanum wheels is that they kinda vibrated the robot as the wheels are not smooth. I know other teams have made shocks and stuff to kinda fix that issue.