It really depends on how far you're commuting, and if it's surface roads or highway.
The smaller XL is fine for about 10 miles of pavement. Wait, let me revise that - the first 5 miles are comfy, the last your butt is numb. Any more pavement needs to be cut with at least an equal amount of dirt!
Top speed on the XL is about 68 to 70. They're geared high.
For an exploration vehicle, they're great (although a converted XR is better).