The ones that have fish on them. I prefer the pro thermals. Only issue I have had is the way they fit the hole late ice. I don't use them for walleye though as I think they are harder to trip then a standard tip up.
I am a huge fan of the Yellow Frabill Arctic Fire tip ups. Very solid for the money. I have been using thermal tip ups a lot the past couple years. I much prefer the black ones to the orange ones due to an easier operation.
The newer pro thermal tip ups are complete junk. Brad, please take this comment back to frabill. The original pro thermal tip up was the best made tip up in the industry and the new design is now one of the worst. The eye guide can't be held tight with a wimpy piece of plastic. I also dislike having to extend/retract the spool every time.
i gave up on thermals many years ago... we cut circles out of 1/2" plywood just small enough to fit in the bottom of a 5 gallon pail, which we always had anyway, and cut a slit in it the width of the tip up shaft from the edge to the middle... paint it black and use it between the tip up and ice... kept the snow out on windy days and really helped with freezing up all winter...