man i'm not trying to be a dick but i've only seen a few subarus with them. it's a very bold claim to say they are "by far the most popular" just because you sell a bunch of them, at least give some reason why they are better.
for the original poster, the best one to get is a recirculating valve. for the least headache stay with the stock one and use the money for something else. just don't go with the txs, they're garbage. i've had one and still have one i won't sell because of it being garbage.