I've been using the Crotip and HF Whistle drip tips exclusively since receiving them in the mail over a week ago. They're both nice, but in my opinion, there's simply no comparison. I prefer the Crotip, which to me is ultimately the
perfect driptip. Despite it's hefty price tag, I would
buy it again, and may even order another one down the road. It is so comfortable to use, looks great, has excellent build quality, and the AMS (air mix system) actually contributes to a better vape. This design provides such a
smooth, low resistance draw, and has added airflow coming in from the sides, making it ideal for lung hits, while not sacrificing flavor at all. I actually find that it improves the taste of the vape to some degree. The tip fits well on all of the tanks I've tried, with the o rings being sized just right. I can't think of anything that could have possibly been done better. It truly improved my overall vaping experience. On a side note, the box it arrived in is really nice, with some heft to it, made of Istrian stone, fully capable of securely holding a 22mm mod.
The HF Whistle tip is nice, but way too small for my preference. It appears to be built very well, but tends to have a loose fit on the tanks I've tried. I'm sure a thicker o ring would remedy that. It does have a nice oval shape that's very comfortable in the mouth. I'd like to see it made in a larger size, equipped with o rings that would enable a more snug fit on tanks.