Almost sixty years ago my very sly father took me to the lawn mower store and let me select the new mower we needed since our Clinton Engine powered rotary push mower died. (
https://en.wikipedia.org/wiki/Maquoketa_Company–Clinton_Machine_Company_Administration_Building)
I selected a 3.5 hp "self propelled" (didn't work at all because it had metal herringbone friction drive wheels which milled the tires down to where there was no contact) mower, with the Briggs wind up starter. ( I was too light and skinny to pull a recoil starter :lol

. We let the salesman sell us a "mulching kit". It was a small sheet metal plate to go over the discharge port. No sculptured anything here. (circa 1959) It was like an extra $1.50
Dad knew what he was doing. Mowing became my sole responsibility. One of the first things (without asking Dad) I did was remove the mulching plate. I have tried mulching twice since then on mowers where it was convenient and have never liked it any better.
I don't like clumps of grass. If I have waited too long (probably why I don't have luck with mulching) and I get some clumps I go over them a second time to "mix them with air". This has worked fine since I got the orange monster in 1999 and works with my Hustler. Worst case if I really waited too long to mow I hit em again the next day after they have dried.
It seems that the suction to make the grass stand up using mulching blades and the air flow to make a better discharge may be mutually exclusive. Supposedly mulching blades used with the discharge chute open don't work as well as regular blades. Maybe others can comment on this. I was surprised.
I do have a tow behind vac that attaches to the mower deck which I used to use to suck up leaves. Since my soil testing showed low side organic matter I will probably just grind them up in the future. Bagger methods are a third choice which has going for it that you can start a nice compost heap. A tow behind really cleans up the lawn.
Anywas I vote for side discharge.