JR,
Panther has a unique system in classification of equipment. It breaks down like this:
"A" unit is a 3/4 or 1 ton van. They receive .77 per mile
"B" unit is a 12' to 16' straight truck that has a Gross vehicle weight under 26,000 lbs. These trucks receive $1.10 per mile.
"C" unit is an 18-24' straight truck that does not have a door opening that will fit two pallets side by side. This truck receives $1.20 per mile.
"D" unit is an 18-24' straight truck that has a door width opening larger than 96". It too pays $1.20 per mile.
"E" units are the Tractors. They receive $1.45 per mile.
Like ABC mentioned, As a team there isn't going to be much of a difference in Loads or revenue between the two trucks sizes.
Hope this helps,
Adam.