Funny thing, I've never seen a Mini with a bullet seater on the side.........wonder why?
It's called a "forward assist". It works in the same theory that if a grarand style action gets caught you can slap the charge handle forward and make it chamber the round. That's a very uneducated observation.
The AR got it's stigma when it was issued during Vietnam. The Government (because they are smarter than the designer) decided that they would try to get 500 yards out of the round so they changed the type of powder from the type that Stoner designed the round for, to a corrosive milsurp powder. The other problem that occured was that the military "claimed" that the AR15(M16) never needed cleaning. Well a lot of soldiers died, not because the M16 was a bad gun, but because the DoD were idiots and told them never to maintain their rifles. The DoD tried to save money, so they didn't acknowledge that the bbls and chambers needed to be chrome lined to keep the shells from sticking to the chamber and to prevent corrosion. (you can write Mr. MacNamara a letter thanking him for being a douchebag and not listening to those who knew what they were talking about.)
Once the AR15 got a chrome lined chamber and bore, got cleaning kits issued w/ a comic book like manual on how to clean your battle rifle, and started using proper powder for which it was designed it begain to excell as a battle rifle. There's a reason it's been in issue so long.
As far as the Mini 14 vs. AR15 goes...
Wieght... AR15 wins The Carbine style varients wieght about 5 lbs. The full size versions wiegh about the same as a Mini 14.
Reliabiltiy... The Mini 14 gets the nod here if you are the type of person that neglects his or her rifle. All mini 14 owners that I personally know leave theirs pretty neglected. "Oh, I can leave this in my truck and put 1000's of rounds through it and never have a jam." to which I say... "Yeah and you hit the target once every 20 rounds or so..." From a real life properly maintained aspect the AR15 will have the same reliablitiy as the mini 14... unless you get a mini 14 like I owned which was a POS out of the box. People who build AR's suggest lubricating the AR15 very liberally. To the point that it's slinging it everywhere when your shooting it. As far as I've heard my frineds who come back from the sandbox say, the Army suggests using very lube on the M16. I call BS. You don't run the engine of your car dry to make it more reliable in sandy conditions. Lube the hell out of it and let it rip.
Accuracy - AR15 all the way... hands down. The cheap AR's that I've built all have held under 1". Others I've shot have consistantly shot 3\4" MOA consistatly. You cant get a mini to shoot that accurately point blank. What about the Target Mini? you ask... If you want to spend 900.00 on a rifle that barely gets 1moa go for it. I'll buy a $600.00 AR that will out shoot it.
Magazines- Unless you going to pay 50.00 for a factory 20 round mini 14 mag your SOL. AR 15's have extremely reliable magazines for 15.00 and milspec mags for less than 10.00
Aftermarket parts - Well AR15 wins here as well. They are the LEGO's of firearms.
So if you want to be a tool and throw away your hard earned money to Ruger have at it... But you gotta remember also that Ruger threw the gun community under the bus at one time saying that "No honest man needs more than 10 rounds at a time."
If you want the best deal for your money get an AR15.
If you want reliablity get an AK.