Hi oma505,
You can see some of my thoughts about the wire grid types of platform/foundations in post #10 here. While they are all fairly similar … I would personally lean towards the ones that have more longitudinal wires and a more evenly supportive surface with less spacing between the wires so there is less chance of the mattress sagging into the wider gaps between the wires over time.
There are quite a number of these types of foundations and most of them have a large percentage of good reviews and they are all rated for over 2000 lbs … but they also all seem to have some that have developed squeaking issues over time or the occasional one where a weld or the frame breaks.
Phoenix