I will not say all MR16 12 volt Lamps are AC, there are exceptions as stated, and I will not claim the DC types will not work from a driver, they may well work from a driver, however some drivers advertise ripple free, which makes one think some are not ripple free and it would seem the ripple does cause a problem or the would not advertise as ripple free.
I looked for the
Varilight data sheet it does not say if ripple free however the sheet does show it powering a LED strip, it does not show it powering a MR16 replacement package, they may work, but question is for how long?
If they fail within 6 months one can expect a client to ring up and complain, but if it lasts 12 months then likely they will just accept it, we saw with the BA22d CFL how these were rolled out with claims of low maintenance and running costs, however compared with other folded fluorescent lamps there output and life was rather poor. The 2D is also classed as a CFL but these work far better.
I personally and one can only work on personally as clients are unlikely to complain if it lasts 12 months, I have replaced 90% of the lights will LED, from replacement tube in a fluorescent fitting, to SES bulbs to GU10 and G5.3 12 volt, the 12 volt lamps are the only units to fail on me, I got some 0.58W units some GU10 and some G5.3 from Pound World, the GU10 worked until removed as they were simple not bright enough, the G5.3 all failed, to start with I blamed this on using AC not DC, but the replacement from Lidi clearly marked 50 Hz and have not failed with 4 powered from a 200 VA transformer I have another 3 spare 200 VA transformers so I would not now worry about using more 12 volt units in locations where there is some dampness.
However one thing I have realised you can float a quartz lamp in water and then allow to dry with no ingress of water, but the LED types are not so well sealed, so although the fitting may be suitable for bathroom or outdoor use, the question arises is the lamp also fit for use in damp or wet conditions?
So I have mounted lamps where they are protected and used 230 volt versions. There is no real need any more for 12 volt, it was used so the filament was thicker and the power supply was regulated but with LED that is not required. So once one has to start swapping transformers why bother with 12 volt?