MR16 refers to the size and type of reflector, I have some SES MR16 lamps, it does not have a length pins to face, I have a GU10 compact fluorescent lamp which is far longer than any tungsten or LED I have. I thing MR16 dates from the cathode ray tube era, when cameras were classified by usable part of tube in 1/8ths of and inch.
I have some GU10 lights where the GU10 holder is fixed, to remove the lamp I use a sucker to turn lamp, and I have others where the GU10 holder is floating and the bulb is held in place with a spring clip, the latter are a pain to renew, but it means bulb length does not matter.
To my mind the MR16 lamp is a spot lamp, and to have spot lamps aimed at my computer keyboard or counter tops means more light where I want it without using silly sized bulbs, so bedroom has pendent and GU10 spots, but most of my floors are not white, so do not reflect well, so lamps are aimed at ceiling or walls or direct to special area, not direct to the floor, my son thinks spot lights look good,
and he has fitted fixed units, but from the bike on wall you can see how high the ceiling is, and the 16 GU10 lamps replaced one 2200 lumen 24 watt LED tube which replaced the original 65 watt fluorescent, at 5 watt each he is using as much more energy as the old fluorescent (80 watt) and at 370 lumen each total 5920 lumen around the same as the old 65 watt fluorescent.
Yes it looks good, and the bike is a good talking point, but lighting wise it does not make sense, I said he should have arranged as the great bear and gone whole way in making a planetarium.
Lighting is not easy, and I have make mistakes, I fitted lighting track and low bay lights in an area with a 40 foot between lamp and floor and it did well, but repeated at 12 foot and it was a failure, the same applies to 2 inch lamps, unless directed at a picture etc, to use them fixed in the ceiling you need a high ceiling, they look great in the show room with a 12 foot ceiling, not much good at 8 foot.
I personally don't like lamps where you can't change bulb, but seems we are being forced that way, the GX53 looked good, but did not seem to catch on, the spread was much better, 5 inch makes more sense than 2 inch, the old 2D was very popular at one point, but fluorescent is on its way out, not a clue why, with electronic ballasts it gives same lumen per watt as LED, lasts same amount of time, and produces less waste, and cheaper. OK has mercury in it, but LED also has some nasty stuff in it too.