By "mouse tabbed" do you mean "tab routing with mouse bites"?
V-Score - from what I can see from google, means exactly that; where the panel is to be broken into individual PCBs, a v-shaped scoring mark is routed into the PCB from both sides, leaving only a bit of material between. It likely results in a smoother edge, an easier break, with less likelyhood of cracks from the break into the interior of the board.
For tab-routed boards, these are just slots routed into the material completely thru the board, with gaps between the slots left to hold the remaining boards in place on the PCB panel. Breaking or cutting the tabs likely results in rough points (while the routed line should be mostly smooth?), which have to be machined away (as necessary). Breaking the boards away or cutting away the extra material might also introduce more potentials for cracking, but only in the immediate area around the tabs. Also, the slots are much wider than v-grooves, using more board real-estate in the design.
As for which is better for 4-layer boards, off-hand I don't really know. My guess would be v-groove if the traces (on any layer) run up real close to the edge, although middle layers might have issues. Whereas the tabbed panels it would only be an issue near the tabs (so if you put anything there, make it part of the ground plane, or a mounting hole - just something not integral to the overall working of the design).
Hopefully someone else can help that has experience in this; until then, just google around for panelization, v-groove, mouse bites, etc in relation to PCBs and such, and you should find some more information that may help you understand better...