If you use the exchange rate Power Converters provides a max speed quarry uses 115 EU/t. An Industrial Grinder uses 128 EU/t. Not much difference, particularly since the quarry will spend that energy just as readily on cobblestone as diamonds; whereas a grinder will only spend energy on useful things (if setup right). Also, additional Grinders are cheaper than additional Quarries (avg. cost of 7.5 diamonds vs. 11, not to mention Quarries need Titanium).
The more auto-mining you do, the better the industrial grinder gets relative to more mining. In general it boosts ore output by about 25-50% compared to a macerator (and that doesn't count extras like diamonds from nikolite). If you have 1 quarry, adding a 2nd would give you a 100% bump in output. Adding a 3rd would give you another 50% boost. At this point, if you consider the bonus items you get from the grinder, I'd say it wins handily. Once you are at a 4th quarry (33% increase in mining), the grinder is the best investment you can make for resource gathering hands down.
Of course, the real value of the grinder is in the extra goodies you get. Highlights include extra iridium, extra platinum, and enough thorium to run quite a few nuclear reactors. If you are deft with a silk touch tool or are using an arcane bore you also get several amazing bumps from using the grinder (i.e. nikolite becomes diamonds).
The extra cost of a grinder relative to other processing methods pays for itself pretty quickly. Also, if properly automated, the grinder uses less power than a rotary macerator. Since you can't really turn off the rotary macerator, its overall efficiency is terrible, even if its draw is manageable.
The one disadvantage that the grinder has that you didn't bring up is speed. No matter what you do, the grinder will always take 5 seconds per ore (same as pulverizer). At a certain point, getting processing times down is more important than block efficiency (at least for more mundane items, I'd still use the grinder on Sheldonite). In that regard, nothing can compete with overclocked IC2 machines. A fully overclocked macerator can handle 100 times more ore throughput than a grinder.