My number one issue against LMDE is that it is built on Debian Testing, which I think is the worst possible way to go with Debian. Debian Sid gives you everything new and fast updates, but it can get broken. Debian Stable is rock solid, you get fairly quick security updates, but as you mention, you are going to get older software. Debian Testing gets broken easily, unless you are pointing to Mint Latest, then it takes forever to get updates, and you still may get breakage.
SolusOS--you get the rock solid Debian Stable, plus you get a lot of up to date software. It is very polished, and ikey seems to be working around the clock on it. For me it was a no brainer. SolusOS all the way. And the SolusOS 2 Alpha 4 has done the impossible, make a gnome 2 desktop out of gnome 3, full featured, polished, and it looks pretty much exactly like gnome 2 in the SolusOS 1 version, amazing.