The Regular Cab version is best-suited to work truck use, with seating for three at most, with the bench seat, otherwise limited to two bucket seats. There's not much in-cabin storage space, but there's always the pickup bed behind you.
The Double Cab model adds rear-hinged doors and a set of flip-up rear seats. There's not a lot of space in the second row, but kids will fit just fine. The extra space doubles as a convenient weather/theft resistant cargo area when not being used for passengers.
The CrewMax is where the Tundra really comes into its own, with a large second row and four full-sized doors. Seating for five is realistic, with ample leg room for everyone. The rear seats even slide and recline. For those who need to transport three or more people on a regular basis, this is the most practical Tundra.
A center console storage area is large enough to hold file folders or even a laptop, the seats are all comfortable and roomy, and general quietness and refinement in passenger experience are great. Where the Tundra falls a bit short is the quality of materials. Though improved for 2014, they're still a full step behind the Ford F-150, Ram 1500, and Chevy Silverado.