Warning: This is OT for the original question, but addresses several questions brought up by both the OP and others. So, if you are the mods/admins, and feel it needs to be moved elsewhere, feel free to do so. I would hate to offend by my OT'ness. (And why, exactly, do we suddenly have several OT police in forums that are not mods/admins? It boggles the mind.)
On to the OT topic at hand:
In my experience, bubbles after using wire cutters are due more to the bubbles present in the mold to start with (stickblending, too heavy of a trace for a swirl, etc). After that it has to do with how hard your soap is when you cut it. I gel my soap, so it is generally hard and ready to cut at about 12 hours. Waiting longer is better at reducing the "snag and drag" effect sometimes seen on the surface of the bars. The only effect I have found directly related to the wire cutter vs the knife is that the knife smooths the soap as it travels down, and the wire cutter does not. But, wire cutters save so much time and effort, as well as giving me nice straight cuts, that I am never going back to the knife, no matter how much I have to work around one tiny downfall.