Check the website or send them a message and tell them (Scott) what you are doing and he will give you the best recommendation.
In terms of MSI, it is fuel only control. If you are running a turbo or blower then a MSII or III is a necessity for the timing control.
First off, I'm not a turbo guy, but I have several friends that are that use MSII's. The largest problem of wrecking your build is lack of timing control under boost. The MSII lets you adjust your timing and fuel delivery based on MAP reading (boost reading). IT IS VERY SAFE for your build in terms of limiting detonation which can be catastrophic at 10+ boost levels. Couple the timing and fuel control with AFR datalogging info and now you can gradually increase/change your fuel and timing control SAFELY. I assume you don't want to be the monthly winner for 'blown up part of the month' in Car Craft
Lastly, for a street/strip build, you will be amazed at what you can do with the tuning for mileage at low boost levels when cruising. I know of a guy with a turbo 4200 straight 6 out of Trailblazer in a mid 50's pickup that makes over 600HP and gets 35 mpg with 4L80E trans that is controlled by a MSIII.
Also, this is pretty neat, you can download an app for for your smart phone to use as a monitor for all of your gauge readings with the TunerStudio software. I believe that if you seen this system in use in person, then it is a no brainer.
There is a ton of info on the diyautotune website. Spend 6-10 hours reading and/or send them a message.
Also the MSII or MSIII can handle both high and low impedence injectors where the MSI cannot.