Depends on what you're painting. I painted an ABS Cowl with Rustoleum Plastic Primer, Yellow Rustoleum, then clear coated it with Rustoleum Clear. After having a month or so to cure during construction, the clear coat softened with about 1 hour of exposure to exhaust. Within a few weeks, the yellow began peeling from the ABS. I finally surrendered, peeled all the paint off, sanded off the remaining primer, and painted with Lustrecoat.

4 months later, the cowl still looks like new.

For me at least, it cost more to use the "cheaper" rustoleum than to just use the lustrecoat in the first place.

I also found the lustrecoat easier to use than rustoleum. I think it has a higher solvent content, or lower vapor pressure solvent. The resultant paint was glossier with fewer coats, and much less likely to run.

Brad