The DE box is a lighter duty version, but will still handle what a stock RB26 can throw at it. When it fails, a DET box is cheap enough to drop in.
The stock viscous LSD's are crap anyway, and should be replaced, so no difference there. Even better, is the DE/E engined cars have the S15 drive flange pattern (3x2), which means you can easily put the S15 helical LSD into it. This is a fantastic LSD for circuit/road use. Much better than most aftermarket diffs.
The five stud conversion is really cheap to do, just need the parts from a scrapped GTS-t. Obviously the wheels/brkaes would need to be changed at the same time. And you save money not having to De-Hicas the car.