Hey Buddy, welcome aboard!
I am also a newbie here but have been on many boards for trucks, boats, quads etc and you will find great info from people with a lot of experience that will save you time, money and head/heartaches...
but... and it is a big but... there is always the my brand is the only brand mentality often coupled with the 'this is the only life I have' crowd.
In a survey of 3,200 foresters 41% favored Husky, 40% favored Stihl, nuff said.
Listen to everybody, sift out the bias and the beer drinking bravado, and buy what is best for you. Remember YOU have to pay for it, carry it and use it. You mentioned physical limitations:BEWARE TOO BIG A SAW! I am a big guy and used to bench over 350# but I bought the 262 and 361 because at 56 my back appreciates a lighter saw. The 20" bar gives better reach. In ten more years I will be real glad I didn't buy the 372!
Like real estate is all about location, location, location so with used equipment it is all about condition, condition, condition! If buying privately look at the guys shop and garage and other equipment... is it well maintained? Good bet. A pigpen? Be careful. Buy new if you can and maintain it well and you know what you've got and over the service life of a good saw it is only a few bucks more a year.
I have a beautiful new MS 361 and it is light, fast and comfortable. I had a 1994 262XP of which the 357XP is the current iteration. I chose the 361 because a) the dealer was closer, b) the out the door cost with the most aggressive 20" b/c was $135.00 better.
In truth, If your not brand blinded there isn't a spits worth of difference between these excellent saws.
Service is a factor but if you do good maintenance you will have very few occasions to need the dealers service, one of the benefits of buying a quality unit in the first place!
As to inner and outer clutches... in 35 years of sawing I have never had a single issue with the outer clutches... and never had one fail due to chips... but I do clean my saw regularly, keep it razor sharp and don't force it!
That's my 2 cents and my story and I'm sticking to it!