Ferment Temp Control: from outside or inside?

Hi. I've brewed over 200 batches and am looking at upgrading some parts of my system. I currently use plastic buckets for fermentation. For temp control, I put the buckets in a large Rubbermaid bin filled with water. For heating, I use aquarium heaters mounted to the side and circulate the water using aquarium pumps. For cooling, I use a separate Coleman cooler filled with water and ice and use a pump to circulate water from the Rubbermaid bin through copper tubing in the cooler. These systems work really well. I've often used a thermometer put through a stopper in the lid of the bucket and oftentimes the temperature doesn't deviate more than 1.5 degrees. Temperature changes occur over the course of an hour, and don't put a sudden temperature strain on the yeast.

However, I want to get away from using an autosiphon and opening the bucket to transfer to keg. I'd like to be able to transfer under pressure. As such, I want to upgrade to stainless fermenters (such as SS Brewtech, or Anvil; however, I just saw ones from Delta Brewing that look promising). However, they use cooling systems inside the fermenter.

Question: Is one form of temp control better than the other? Meaning, from the outside or the inside? I would think the greater surface area of the outside is more gentle; however, I'd guess if there was an issue of running really cold glycol (from a DIY glycol chiller... potentially a cool project!) through tubing inside the fermeter, they wouldn't be as popular. Same with the heating belts: they're much warmer than the water system I use, if they were harmful I would guess they wouldn't be as popular.

Thanks for your thoughts.

 

Disregard this. I remember my high school chemistry: you're not cooling the wort/beer as much as you're absorbing and removing the heat.

Too late to delete the post.