I'm in my garage flooring R&D phase as well.
I have samples of RaceDeck Freeflow, RaceDeck Diamond and Swisstrax Ribtrax (Similar to Freeflow).
A few observations...
Anyone who is concerned about the hollow or "click-clack" sound should consider the open face Freeflow or Ribtrax design as it significantly reduces the echo sound associated with the solid surface tiles. I performed a test where I dropped a quarter on each tile. The sound when the quarter hit the RaceDeck Diamond was very loud. Sort of like dropping a quarter on a pergo faux wood floor. When I dropped the quarter on the RaceDeck Freeflow tile, the sound was a lot quieter and more muted. Sort of like a softer, rubber surface. So if the hollow sound is an issue for you, the Freeflow is the better choice as the sound will be a non-issue on a full floor. In fact, I bet the overall garage echo will probably be muted as the floor tiles will probably help absorb sound.
IMO, the Swisstrax product is geared more torward commercial or industrial applications. It is a beefier product, larger in size (15.75 inch squares vs. 12 inch RaceDeck squares) and thicker as well. While this is good, I also noticed it was more difficult to vaccum up dirt and other garage floor junk through the Swisstrax than it was the RaceDeck. You can slightly bend the smaller RaceDeck Freeflow tiles but you cannot bend the larger Swisstrax Ribtrax tiles at all. Also, the Ribtrax grid-like pattern seems to show less of the floor underneath than the RaceDeck Freeflow tiles probably due to the thicker tile and the additional cross-beams underneath. Unlike the RaceDeck Freeflow, the Swisstrax Ribtrax also have an X-pattern that appears on the top of the tile which IMO sort of distorts the 3D cross-pattern visual effect of the tiles so I personally like the looks of the RaceDeck Freeflow better.
What I cannot understand is why Swisstrax decided to engineer their tiles in such odd configurations. Why 15.75 inches?! IMO, it makes it more difficult to measure out and design a floor. Plus their other style tiles cannot mix/match and they come in different sizes based on the design. The RaceDeck tiles can be intermixed. It would be a lot easier comparison if I was comparing a 12" RaceDeck tile to a 12" Swisstrax tile.
The RaceDeck tiles also tend to lock in a little tighter than the Swisstrax tiles primarily because their hook and loop tabs are larger than the tabs on the (larger) Swisstrax tiles.
It makes for a really tough decision, however I think both brands are high quality and will work well for any residential application. The Swisstrax will be more expensive per tile, but you will need less of them to cover the same square footage. However as mentioned, they are beefier and feel more commercial. I think their colors are a little more muted than RaceDeck also. The RaceDeck beige is almost an exact match to my existing floor epoxy and I like their graphite color as well. The Swisstrax ivory is the closest to the beige I can find and it has more of a yellow-ish tint and their gray tiles are not very dark compared to the RaceDeck graphite. I guess it comes down to a matter of personal taste.