I just played around with this emu. I've been meaning to but never had a strong reason. In the 'video' properties in-game, you have to select 'enhanced' (which is D3D7), and then '3D projection'. It's interesting in that it gives you a sort of monitor inside your monitor effect. It also carries over to the fe part, which is cool.
Effect rendering is equal in quality between 'basic' (DD) and 'enhanced', and stomps regular Mame. (I think it only gives you one type of scanline effect - the real kind.) As well, in the enhanced you can select scanline intensity, although this has an effect on the overall brightness. As well, the latest version seems to be far less resource hungry than Mame, as I've been writing this and flipping back and forth to FB while it's running 'attract', and no peformance issues. The latest Mame (using Ghouls and Ghosts) dogs my computer a little, and that's without using effects.
Some in-game feature differences seem to be: no tab or tilde menus, no pause. And apparent draw-backs are that it can't do complete fullscreen and isn't cab friendly (page menu bar and Windows task bar are visible, and all settings are done in-game through the menu, upper-left).