Subframe connectors for a driver/cruiser, necessary to weld to floor?

The ones that weld to the floor do a much better job at boxing the frames in. The old school ones just use box tube to connect the front and rear sub frames together. It does help but not as much as the ones welded to the floor.
For a mild street car the old school ones are fine. Save your money instead of buying them and make your own from box tube.