Is this for street or strip?

For street use I'm in the 727 and be done with it camp. Went through a few 904s including one where the converter snout broke off and ruined the rest of the trans.

I have a TCI streetfighter 727 in the car with a PTC converter and feel way more confident in its durability. For a strip car where worst case scenario is having to push it to the pits and load it onto a trailer, build all the 904's you want. They are definitly lighter, but don't kid youself that they are as tough as a 727 with equal quality/type of parts in each. There's a reason engineers didn't put 904's behind big blocks.

As to the violent first gear thing, so far as I know all 727s have the same gearing. The people telling you that may be confusing them with later model 904s (999?) that had a lower first gear. Behind a stout motor with low rear end gears it would make for a pretty violent launch followed by a pretty boggy 1-2 shift because of the wider ratio split between the two.