The chili pepper is cheap and gets horrible reviews for durability on Amazon. I don't know much about the Metlund.
That said, I have experience with neither. However, I will suggest you consider Redytemp (and a dedicate return if that is an option). They use a proper, heavy-duty, replaceable Taco stainless-steel pump. It is a standard unit, if there is such a thing in plumbing. Should you ever have trouble in the future the pump can be replace, by itself, without tearing apart your plumbing. Also, if you have the constraint of using the cold water line to recirculate, they offer a proper positive shut off valve so as not to overly warm your cold water line.
Yes, you get what you pay for. And I do have a Redytemp unit with my Noritz NR1111DVNG. I really like it. It is on a timer, as well as Leviton momentary rocker switches in the kitchen and bathrooms. It turns itself on at breakfast and dinner. The rest of the day it is on demand from the switches.