I ride gears, fixed and single speed. All have their niche.
I use the 67" SS for short loops and like the work out it gives me. Slow strength training on the hills and fast cadence training on the flats/descents. This bike used to be fixed, but there are too many descents in Kent to make it enjoyable. Have ridden this as fixed for the Castle ride (100 ml), but the last few miles killed me in the shoulders as you can't quite relax as you would do on a geared/freewheel bike.
The fixed is a 95" set up for 10 mile TT's. I only ride our club's evening 10 series now, so never long events, although in the past have ridden a 50 or two on a fixed. A few seasons ago, I was experimenting and comparing a fixed bike with a gears bike and by the end of the season, only 20 seconds separated the two bikes. So now just use a fixed for TT's as it is just simpler and I think on the "perfect" night, will be quicker as it is lighter and has less drag than a geared bike.
My geared bike, which started as a 2x10, was converted to a 1x10, with a 40t chainring and I am using this for the longer leisurely and more hilly rides and find changing down and keeping the revs on the hills a luxury.
One other reason I have for riding a fixed for TT's, is the fact that my Dad rode fixed as did everybody in those days and he achieved a "5" for a 25 and I promised myself that I would wait until I could beat his time before I switched to gears. I am still waiting, although I am 37 years older than he was when he did that ride.