Having previously owned and ridden a Matchless 500 single back in the day, sixties, and back in some not so distant days, seventies and eighties, owned and ridden 2 SR500 singles, I can speak from experience. In stock trim, the matchless was as fast or faster on top speed as the Savage-S40. The Savage-S40 may have a tiny edge in accelleration. The SR 500 was a tiny bit less on top end and a tiny bit less on accelleration.
In cornering, the Matchless has it hands down with the Sr500 a close second.
In braking, the SR500 with its' disc brakes was the Quickest stopper. with the Savage-S40 a very noticable bit less able. The Matchless with its' drum brakes was made to go, not stop.
Riding position was best with the Matchless, and second with the SR 500. Savage -S40 with its'cruiser position does not give the ability to transfer body English neuances as well as either, and makes standing up on the pegs more difficult over rough surface.
Gas milage is about the same for all of them with riding habits being the determining factor.
All three had too small a fuel tank although the matchless was the largest capacity.
Both the Matchless and the SR500 used a separate oil tank and a dry sump system which made changing oil easier. On the Sr500 the bike frame was the oil tank, a system I do not approve of anymore.
While it does to some degree act as an oil cooler, if you get contamination such as metal particles in the oil, cleaning the inside of the frame is impossible without taking the bike completely apart so you can shake it with solvent inside.
The Savage -S40 has far less vibration than either of the others and is more maintainence free than the others.
Verdict, If you want to canyon race, choose the Matchless or the SR500. If you want to put long miles with little trouble choose the Savage -s40
Matchless REQUIRED that you know the starting drill concerning manual spark advance and manual compression relief. Also you had to understand theubiquitous Amal carburator and its'tickler button.
SR500 merely had manual compression relief to deal with.
Both were kick start only.
All three are very handsome looking machines.
Does this answer your questions?
Phelonius