A regular cab 2.7 will probably get better gas mileage than an extra cab V-6, but you're right, power is the name of the game.

Personally, if it were me, currently owning a single cab truck and having driven an extra cab Tacoma on a long trip, I would rather have the single cab for off road trail use, just because the short wheelbase makes turning around on tight trails and roads much easier. I'm thankful for having a short wheel base truck when I'm on a ledge road that's barely wider than my truck and I need to turn around. But on the other hand, there is absolutely no room whatsoever to store anything in the cab. For that reason, I'd rather have an extra cab for a daily-driver.

As for motors, I really like the 2.7 for it's ruggedness, simplicity and economy and it's such a good motor, Toyota carried it over for the new Tacoma. But, in the end, I'd probably choose the V-6 for the extra power, if I had a choice.