I had built a new bay for my Mustang a couple years ago and am still struggling with what to do with the floor: paint, tiles, or mat. None are the 'perfect' solution.
I'm going to assume by interlocking, you are talking about the ones that kind of look like mini grates (i.e. have holes in them and are not solid). With those tiles, the biggest issue would be spills. You want to make sure you have a tile that can be 'easily' taken up from the middle, to wipe the affected area. Depending on the amount of spillage and slope of the floor, could be quite a few tiles. You have to clean the floor and the tiles. And, as mentioned, there is the issue of dropping things.
With paint there are SO many choices. The two biggest things with 'paint' is getting the floor really clean and how much mositure that may come through the floor. If there is too much moisture, the paint will eventually lift.
The issues with a mat is find the size you need (typically too small or too large). You can cut then down if too large, but then you are paying for stuff you will not be using. And the other is moisture getting trapped under it.
My opinion is that 'paint' would be the nicest, but there is just no way to know how long it will last. I think the map is a good compromise because it can be easily taken up, and you can see how much an issue moisture may be. And I believe they are a cheaper option that tile.