Since we are nit-picking here, your cheat tiger actually makes the game slower than it should be. Overclocking the second processor isn't necessary and eats up a lot of processing power.
Frameskip 1 simply saves some processes by not drawing the screen as often. It just squeezes a spare fps or two out of your system. Yes the 3d models are still calculated in the processor, but they aren't drawn and since drawing is done in software in mame, you will see a slight difference. But all in all, you could have it on or off... it's the 25% processor underclock that makes the biggest difference.