I find cost quartz to LED is rather hard as they are not straight like for like. With 12 x 35W = 420W that is a lot of heat, so one would be looking at air conditioning units to remove that heat. Do you include the cost of the AC in the calculations? likely not, but you will likely include the benefit of living in a cooler room and also not having to renew the bulbs as often. But how does one allocate a cost to discomfort with hotter room or man hours changing bulbs?
The MR16 when converted to LED no longer is 16/8th inch across because it has cooling fins, the 2" round dots were small enough to start with so it really needs something to defuse the so it has a better spread. Pod type spot lights shining onto white walls can work well, but fixed shining onto darkish floors the room can look like a planetarium.
With LED lighting there is nothing to stop fitting flush mounted units 12" diameter rather than 2" as it does not need to get rid of the heat from the back of the lamp, using 12" rather than 2" means no need for diffusers to spread the light. So a light like this
will light the room far better than the silly spots for the same wattage. Exactly which lamp suits the room I don't know, but likely using larger size lamps instead of dropping 420W to 60W you could drop to 30W because of the spread of the light using 12" lamps. Also likely 2 or 3 fittings instead of 12.
Room lighting needs some design, just matching lumen is not enough, I used two standard lamps and two ceiling lamps in my living room mainly as I don't want to mess around in the ceiling space fitting extra lamps, plus the standard lamps are only used for reading, when watching TV I can just lean back and switch it off. My kitchen I have reduced the light in one half from 5800 lumen to 2400 lumen simply by swapping a fluorescent tube to a LED tube, but other side I need the extra light so fluorescent tube stays. The main reason the fluorescent tube light works so well is it's size, it's 5 foot long with a defuser on it so no corner is dark, great for kitchen, but would look horrid in a living room.
Using a standard five bulb fitting with the bulbs facing up so they reflect off the ceiling or with bits of glass to spread the light works well, remember most LED bulbs unlike the old tungsten shine very little light to the base of the bulb, so bulb facing up with a light coloured ceiling or down with a dark ceiling can really change how much the room is lit.
If you think about it and design your lighting to suit the room with a balance between looks and functionality you can get a really good result using LED lamps, but just throw it together and as one would expect the results are not as good.
