The Tundra has always been considered a full size truck. Now, if you want opinion, then no, I don't quite consider the first gen on equal footing with the Big 3 pickups, but it was designed to be a competitor. The body style makes it look smaller. Shorter bed sides, short grill, etc compared to a truck of today with there 3 ft giant grills. Now, back to fact. They didn't conform to some american standards. It came in a full size 8' bed. In the early double cab version, it was longer than the F-150. However, don't buy a standard bed toolbox and try to install it. It is about 1" narrower than the standard ford and chevy bed.

As far as HP, it was weak. By todays standards you can go buy a 3.5 GR Kai camry and have much better fuel economy and about 60 more HP than the big 4.7 UZ V8 in those (Modern VVTs and dual injection is great). I think they were trying to offer an alternative to the big 3, hoping to break into the market instead of just trying to outdo them.

You want to know the real difference in the first Tundra vs the second? Both are American made vehicles. However, the first gen was a Japanese designed vehicle. Why in the world Toyota would let the Japanese design a pickup truck?...There are no pickups in Japan.
The second gen is a Toyota America vehicle, designed, built.