Considering making my FiST a decent track day competitor but also I know the stock rad isn't really that good in terms of keeping the car ideally cool. My car stayed cool on my first track day but it was also a nice 60 degree day and not the 90 degree days that track days are usually at.
I've heard good things about both brands but I want to get other peoples opinions on it.
They are both good radiators. The Mountune radiator is thinner, but flows less since it is a more restrictive internal design with a dense fin layout. The Mishimoto radiator is thicker with a thinner fin layout. It also flows more water due to being a different design.
The Mishimoto radiator has a better thermal rejection due to their design, but is heavier due to its larger thickness and larger coolant capacity. The Mountune one is a slimmer design that weights less, but it flows less coolant and has less ultimate cooling capacity. Both will serve your needs.
I have a lot of mishimoto products (J-Line FMIC, Radiator) on my car and they are pretty good. I have had them send me a schematic (ACTUAL SCHEMATICS) to their product when I lost an important part in storage. Since it would have cost a lot for them to ship me it, it was way cheaper to have it made by a local machine ship. Awfully nice of them.
Likewise, have had good experience with Mountune (MRX Turbo, BOV, Accessport). I had one of their v-band clamps shatter at the bolt. They had lost/forgotten the replacement I made over the phone. In response they sent me two replacements, over night shipping, for free. That was pretty swell of them considering it cost them about $70.
I wouldn't look at the BBB for anything. Their memberships are costly; companies basically pay BBB to get better ratings. That is how it works.
