Well with me it was all of the the things you mentioned. However, I believe the number one reason I liked the 727 so much as a pilot was its versatility or ability for using short runways. It really was fun to fly, but I've flown many other aircraft that I enjoyed flying more.
That being said the 100 series with the -9 engine was much more enjoyable than a 200 series with about any engine, with the possible exception of a full Valsan conversion 200 with the 219 engines in the number one and three positions.
Now don't get me wrong, on a hot day in Denver on takeoff you never seemed to have enough runway. On the other hand I always enjoyed landing and turning off the runway in less than 3,000 feet. Also for a week I flew a 200 with -7 engines, if that had been the only 727 I had ever flown I would have hated them.
I never had the chance to fly any series of 737s, but speaking from the point of view as a passenger and from watching them land and takeoff I really don't see that the 737 has better runway performance than the 727.
Another reason I liked the 727 was its speed. Not as fast as say a Convair 990, but except for the Concorde there were not too many airliners the 727 could not pass. The slowest I ever cruised the 72 was .80 Mach, unless ATC slowed me down for a 737. When in a hurry, like getting home for the weekend, all of us cruised around .84 or higher and always rode the barber poll on descents. (And yes you could not hear yourself think in the cockpit at high IAS.)
Anyway, I have a little over 7,000 hours in the 727 and truly do miss flying it.
(But the big boys tell me that if I liked the 72 so much, I would have loved the L-1011 even more. Probably true, as all of my most enjoyable flying was in three engined aircraft.)