Ive had a side mount, an HKS TypeS FMIC, an XS Power 4row FMIC and a Greddy VSPL 3row FMIC.
Anything is better than the side mount but thats pretty much a given. Out of the others, and this purely out of quality and value for money, Id say the Greddy wins hands down. Bearing in mind that the latter three were aimed at being future proof in terms of engine upgrading.
HKS typeS = lot of money, and when you open the box you do kind of wonder where all that money just went. Very good fit, eventually, after a lot of mucking about. Bit small, so maybe limiting in the future. Old design. Very thin silicone connectors.
XS Power = cheap as chips for a big cooler. Niggling little manufacturing issues like brackets not always lining up. End tank design notiecably different. Custom pipework needed, where do you stand if it comes back wrong.
Greddy VSPL = right on the button. Big price tag, but worth it. Excellent pipework. Complete kit. Very good quality components. Constantly evolving design (kit gets tweaked every so often) fits first time. Pretty much future proof.
Just my 2p worth. Hope it helps