Despite what Bobby Flay say's it doesn't taste like a spicy raisin. Chipotles are smoked jalapenos. For reasons I don't quite understand, other than that flavor becomes more concentrated, it really pumps up the Scovilles.

Thanks!! Great advice!

I prefer it for it's smokey more complex flavor. It is much spicier. When I make chili I always use both but I had to pick one, i'd always pick Chipotle.

I find chipotle the flavor of choice for complexity as well as heat. Starting with less and tasting and adding is good advice.

I do that sort of substitution all the time and it works just fine. It'll taste different, but you'll have a similar result. Take into account: chipotle is much hotter than ancho, so depending on your heat tolerance, you may want to scale back the amount (I'd start with a quarter of the quantity and work your way up). Also, chipotle is smoked; ancho is not.