I sold my C4 for $500 and have regretted it. Fun one to have and a good way to send 9mm 100yds. Some folks hate the look. Cleaning never presented too much of an issue.

Regarding your AR choices. I own 5 Bushmasters and no real issues. I'm a paper killing civilian. However, it's better to cry once than cry twice. I have since over the last 5-6 years done a ton of research shooting and wondering around this forum and others. Of yours listed I would go Colt.

Not bashing Bushy just saying if I could do it over I would probably go big. I'm a DDefense fan. Back to the C4 though I bought it used for $450 and someone lost big on that deal.