hmmmm, "best"....???? Thats a loaded question! :)  Depends on the weather and activity in my opinion. I have a pair of lighter Columbia's that are absolutely fantastic that I wear often. Have no idea about the thinsulate rating though. I find that I wear them more often than not but I generally find myself moving alot. When I go with a bunch of people and its tip-ups and shoot the crap drinking beer with the buddies kind of a fishing day then I will wear some 2000g thinsulate Sportsmans guide boots. (wouldnt want to do a 20k ruck march in them but they are light for the bulk of them) Heck sometimes I wear my old sorels. Boots like clothing comes down to the activity. Sweat is the killer. Breathability I think is key. Sweaty feet=cold feet. Its hard to find that versatile boot for all situations. I think a dry pair of socks for a quick change after a long hike at times is the best answer. If yer not doing alot of walking might not be an issue. I just try to match the boot with the activity. Bottom line, waterproof, can breathe to help dry the sweaty tootsies and a comfortable level of insulation.  (just my 2 cents) be safe out there.

I have been wearing LaX Ice kings for the last years and have been very happy with them. I wouldn't want to walk 5 miles in them but good for ice fishing and deer season.

Just thought I'd chime in on this.  I bought Baffin Eigers last year.  After one season I will say they're awesome boots.  My feet never get cold and the boot is really lightweight.  It is a large boot but very comfortable to wear.  I bought a new striker suit this year and they fit over the boot, but not by much.  Also I wear a size 10 but purchased a size 12 in the baffins.  Allows for sock room and not tight as that's what always makes my feet cold.  They also don't rub my heel from being too large, even at two sizes larger.

Really depends on your style of fishing.  If you just sit in one spot and don't move much and don't have a shack to warm up in then I would want the warmest boot you can get, I would not worry about weight.  I tend to hole hop and a lot of the lakes I fish I have to walk on so my Lacrosse Aeroheads I bought for hunting are warm enough.  If I can drive on the lake I have my hub style shack with a heater so again the hunting boot is good enough.  It doesn't take that much moving around to keep warm even on cold days.  My holes are usually within 30 yards of where I set up and that little walking from hole to hole does wonders.  I get colder sitting in a deer stand when it is 30 degrees than I do ice fishing. And the Aeroheads are 18" tall so you stay dry and don't get snow over the top of them.  I would try what ever boot you currently own and decide for yourself if you need a warmer/heavier boot.  But I prefer a lighter boot because of my style.

"Best" boots and warm clothing is really subjective and based on the physical traits and conditions of those wearing them.

I'm 52 and have good circulation, a dude who's 38 may be worse off than I. So the same boots for each of us simply won't be the same.

Socks that wick moisture are key.  I have been fishing in my LaCrosse Ice Kings for well over a decade and they keep my feet dry and warm.  But they are far from light weight.  Maybe newer versions are lighter.  The boot I'm interested in is the boot that Ice Armor/Clam has recently come out with.  Looks like they're made specifically for ice fishing.  They're rubber and have a removable wool liner.  Rated to -40 degrees.  If it's any colder than that, I'll be in my chair watching something on Netflix.  I have not seen any reviews on them yet so I'll probably just wear the old Ice Kings until next season when more info/opinions are out there.

Just my 2c

it all depends on the person to and socks. Start with good wool socks and go from there. My feet sweat so i wear lightweight smartwool socks to wick the moisture. Then i wear 800 gram thinsulate irish setter mountain claws. They are under 5 pounds for the pair, fit my feet great and have a wide toe so i can wiggle my toes to keep circulation in them. So for me that is the perfect boot. I had some rocky blizzard stalkers that im convinced one boot was missing thinsulate in the toe because two of my toes would always get really cold. It all depends on the person really. Also carry extra socks incase your feet get wet or really sweaty. Then you can wear dry ones and dry the wet ones on the heater. 

In 32 years on the ice, I've tried several different boots. I found the white bunny boots to be the warmest, and have worn out two pair had thinsulate booties over cotton socks, and felt innersoles.As warm as they are, at times my feet got chilly, Last year I wanted to try newer, lighter technology. After much research, and reading of reviews. I went with Baffin Impact boots. With just one pair of cotton socks, they are the warmest, lightest, most comfortable boots I've ever wore. One of these boots weighs about the same as my pair of bunnies.

Hands down, Baffin Impact boot. I purchased a pair this year and never even had to think of wool socks. I've been wearing just my regular socks all year. Light weight and rated for 145 below zero! Tested in Antarctica. They may be pricey but I'll never have to purchase wool socks again. My feet don't even sweat in them.

I use Cabela's infernos with Smart Wool socks.

Add these and you have a nice setup for a dedicated ice fishing boot. I only wish they had the Boa Lace system available when I bought them because I love those on my wading boots

http://www.gripstuds.com/Boots.php