IMO. If you drive mostly on road then get the street one. If you hunt and go off road alot then the more aggressive tire is for you. The mpg diff will be so insignificant it realignment relevant. Just go with what you like better.
I personally didn't see any change in my pmg when I upped to the 325-60-18. That a load range D tire and they are heavy.

 

i ran 275/70/18 terra grapplers and averaged 14-14.5, i just upped to 295/70/18 trail grapplers and im averaging 13. i know they arent the same size but i figured id give ya the food for thought, bigger and heavier and i only dropped 1 mpg, equal size i doubt youll see a difference

 

The Trail in a 33" LT295/55R20E is 73 lbs, and in a 35.5" LT295/65R20E is 78 lbs. (according to DTZ), but didn't see a 34.6 LT295/60R20 there, but by extrapolation, should be around 75 lbs. They list the LT295/60R20E Terra A/T as 69 lbs. Not significant differences in these sizes, but for some like a LT295/70R17D, the A/T is 55 lbs. and the M/T LT295/70R17E is 71 lbs. The D load capacity tires tend to be lighter.

 

just installed my 295 70 18 trail grapplers. have only about 50 miles on them, but cant even get the instant mpg gauge to go past 20 for even a second unless i am completely off throttle coasting!! i used to maintain around 20-25 on the instant gauge, flat ground, no wind and cruise locked at 45. something is going on... maybe they need to be broken in lol!

 

What's going on is they're around 30 pounds a piece heavier than stock tires.

According to Discount Tire, that size of Trail Grappler weighs 72 pounds. http://www.titantalk.com/forums/discount-tire-direct/105862-trail-grappler.html#post2015013

When I ran my Toyo M/Ts that were 73 pounds, (and the next size up over my stock tires which were 43 lbs.), my Titan lost 2 mpg.