I had to look this up myself and thanks, Gloria, for the neat info on wikipedia! I love this topic of pimento talk.
. Here's another informative article:
I do need to give credit to this so here goes:Published January 1, 2007. From America's Test Kitchen. (Cook's Illustrated).
What's the difference between jarred pimentos and roasted red peppers?
Fresh pimentos are thin-skinned, heart-shaped sweet peppers with a slightly bitter, aromatic flavor reminiscent of paprika (a spice made from pimento pods). Jarred pimentos have been boiled to remove their skins and then packed in a brine of citric acid or vinegar.
Jarred roasted red peppers can be made from a variety of peppers, including pimentos and bell peppers. As their name suggests, jarred roasted red peppers are roasted to remove their skins and then packed in an acidic brine.
We compared nationally available Goya pimentos with our favorite brand of roasted red peppers, Divina (made from Florina peppers, a type of pimento grown in northern Greece). Straight from the jar, the Goya pimentos had a "pungent," "complex" flavor with some bitterness and astringency. Their texture was soft and slimy. The Divina roasted red peppers, on the other hand, had a smoky, sweet flavor and tender, toothsome texture. When we sampled red pepper dip and arroz con pollo made with both peppers, opinions were split; some tasters preferred the briny pimentos while others favored the smoky red peppers.
If you're only going to buy one product, we recommend the sweeter, smokier flavor and firmer texture of roasted red peppers, but pimentos can be used in place of roasted red peppers in many recipes, as long as you don't mind their slightly bitter, briny flavor.