Cools is talking there about a multi-sync unit, as you'll know. Multi-sync arcade monitors quite often provide a not-too clean picture at 31 kHz, which indeed benefits a picture with simulated scanlines effect/black-frame insertion. Though, in my experience (which is not much with these, actually), it's not better than the actual 15-kHz display.
It much depends on one's preferences, as well as the monitor's behaviour. For instance, some people are crazy about high-end 15-kHz BVM displays with over 600 TVL, in which case a good VGA monitor at 640 x 480 with simulated scanlines effect (or black-frame insertion, since it'll support 120 Hz) will show a very similar result. I myself find that too unnatural. I'd say if you're used to old arcade monitors, keep a true 15-kHz display at hand. 39'' 480-P is not something I'd reject, though; there are many things to emulate/play at that res.