You are going to want the most scalable, reliable and easy to maintain solution.
The advantage of G-SATA is its portability and size. However, if you want to increase the storage, or the number of drives raided together (for higher throughput) you have to string multiple G-SATA units together. You have multiple power supplies, a tangle of leads, and more things to go wrong.
Using an enclosure that has growing room for extra drives, a decent onboard power supply (rather than the G-SATA bricks)and easy access for upgrading/replacing the drives to me seems a better option.
These are just observations though, as I have no direct experience of these solutions.
Hi Greg, I've been using the Mac Guru 5bay drive with port multiplier card into my sonnet4x sata control card. I also purchased the roll your own version. The build was incredibly fast and easy and sometimes you can find deals on drives through mass drive retailers that Mac Gurus couldn't ever match. I used 5 500gb seagates and ended up with about 2.36 usable terrabytes. The drives have been operating flawlessly for about 4 months now. I'm using M100 8.2.2 Dual G4 1.42ghz 1.5Gbram OS 10.3.9 cutting at 300kb Beta SP/DV Cam/DV. Rick is the owner there and very courteous, friendly and extremely knowledgable. There product is very good. I can't speak about G-Sata. I'm sure they also make a good product - but - I've never had customer service like Mac Gurus before. Best of Luck! Kind Regards, Chris