Tom Sherman wrote:

What is the strongest cage on the market?

Unknown. Based on looking at the construction quality, I'd say the Forte
Performance Terra Lite Stainless MTB Cage is one of the strongest.
Better design than the King Cages in terms of how the mounting plate is
welded to the tubing.

When I lay my lowracer down on the non drive side, it rests on the cage,
so I tend to break them frequently.

The solution isn't a stronger cage, which will transfer the force to the
braze-ons and damage the frame, especially if it's an aluminum frame
with Rivnuts.

I'd buy a set of
"http://www.lickbike.com/productpage.aspx?PART_NUM_SUB=%273242-00%27"
and mount them snug, but not so tight that they can't rotate around the
tube (assuming it's round tubing!).

I use these on one of my folding bikes where it's necessary to rotate
the cage out the way when folding the bike.