looking for gun guys opinions

[Spades of Columbia]

I'm going to start a SBR projects in the next few months and cant decide what i want to build.

My first choice is to try to build a 552 commando like firearm. I can buy a Sig 556 Patrolman and then have the barrel cut down to a 8.9" barrel and then throw on a 3-prong flash suppressor.

Or I could buy one of ATI's new MP5 designed AT-94 in 9mm. Then have the barrel cut down to a 8.9" barrel and then slap a collapsable stock on her.

Or lastly i could purchase a RONI system for my glock 19 and then have some extra cash for a improved scope likely a ACOG 1.5xx16.

Just looking for pros and cons on what is worth the time and money?