Hakko's CHP flush cutters are superb, and inexpensive (they go for about $10 or so). They're superior, IMHO, to the earlier Xuron cutters, on plastic. Hakko is the US importer (they sell soldering irons) and the CHP tools are made in Italy. Several sizes, for metal wire and now they have a model specifically made for plastic, too, the model TR-25-B. And they have wonderful handles, too. I have two sizes of the earlier cutters, the TR-25 and a smaller one with a thinner smaller head for tight clearance work.
Flush cutters have edges that match up, while bypass cutters (the Xuron are extremely fine bypass cutters) work differently. The bypass cutter edges literally don't match, but pass by each other. The edges on the latter last longer because they don't touch each other. Each type leaves a different result on the part you cut, and it depends on the material being cut. While the Xuron cut very close, they do leave a slightly raised square stub, and the flush cutters leave, if anything, a pointed stub. Now these stubs are extremely small, and on most plastic the flush cutter, IMHO, leaves less or nothing to trim. These remnant stubs are less prominent or virtually invisible to the naked eye if the cutter edge is very acute; I cannot feel any remnant when I use the CHP cutters, but I can when I use the Xuron. Plastic is much softer than metal, so cutters with more acute edges are preferred on plastic. The more acute the edge, however, the shorter is the edge's lifespan.
Any of these cannot really be resharpened when they get dull, but at $10-20 a tool, they're easily and cheaply replaced.