We've done a little small 3-gun at TMSA but are most known for our TacRifle matches (and of course our range has a lot of IPSC). Rifle will be the factor that makes you decide between various options. We've been doing rifle a loooong time and have gone through all the fads! Belts, Drop legs, Vests, Plate Carriers, etc. Through all the color fads too, black, OD, dessert tan, multicam and now getting into "urban grey". Yup this is tactical fashion, urban grey is in!
A belt alone is not always faster than all other combinations of equipment because of bad Canadian laws and size requirements (way easier in the US with normal capacity magazines). Especially with 5 round rifle mags (yes many people run pistol magazines, but not all and technically the laws we must cater our rules too). We typically run a 26 round rifle stage which is 5+ rifle mags. That can be unwieldy to manage on a belt alone, let alone with 20 shot shells and 3 handgun mags (and maybe a multitool, or other accessories). In the US (ie: Custer) they run 2 AR mags, one primary 30-60 round and one backup 30 round in case of malfunction, that's it! Easy to fit on any belt system.
But up here with 5+ mags, guys who have the belt space for all this in a neat flat layout generally have a little more girth in which case they aren't that fast when measured by overall match standings. Guys who are in amazing athletic shape sporting a 32-34" waste can't fit all that crap on their waste without double stacking stuff everywhere. Double stacked AR mags, double stacked shotshell holders, etc. Makes you wide and awkward and more likely to fumble a reload and grab the wrong thing. I've seen guys try to put a pistol mag in their AR or try to put the but end of a mag in their AR etc... all solvable with practice. But I'm just pointing out that its not the automatic defacto winner.
A vest easily doubles up your capacity and can be removed when not needed to split up your gear/weight between belt + vest. The guys who do run a belt end up adding a drop leg thigh rig with extra AR mags (2-3 on the belt flat, 2+ on the thigh flat). This may be faster because of lower overall weight and maintaining low profile. But ultimately 'Cyanide Ride' is correct - do what you like and what works for your body type and then practice! No two people are shaped the same or are in the same physical shape - your mileage will vary. One size fits all solutions don't work.
Several of our top placements at matches are guys with plate carriers and full gear that many would say is "heavy" or "bulky" but it works for them and they practice. But one of the guys most frequently in first place is a belt + drop leg thigh rig. But he also runs like mad - so is it his equipment, or is it just that he's in good shape? (He also has one of the top custom built fully loaded ARs, so that's another factor in the placements).