IMHO pump tracks are more designed for full suspension MTB's hence the pumping motion to create momentum. To me it sounds like you need more a bike that fits your lifestyle needs being fitness and transportation.

24'' BMX are great for cruising and decent for jumping but difficult to do tricks even basic ones like bunny hops. So this is your bike if you are looking for something bigger that will get you across town and still feel like a BMX.

20" Well these are the do all for tricks and jumps and the essence of BMX. But modern geometry on 20" BMX bikes sucks for using it for transportation and cruising. For one it's really difficult to sit down on the seat. But If you want to learn how to bunny hop and do rail grinds pick this one.

Personally I hate to admit it but a 26'' MTB Dirt Jumper with shocks might be the best of both worlds for you.