Whats the difference between the Smart Carry holster and Thunderwear holster?

They are both a bad idea. In my day we called that style of carry the castration carry..Having a loaded gun just above your groin is not a good idea....

Don't listen to this. These people never owned one or else they'd know the muzzle does not point at your groin. Smartcarry and Thunderwear are basically the same. I've owned both at some point and while not a perfect everyday holster, they do make a great extra holster for discreet carry in a non-permissible environment. I used to wear mine when visiting my inlaws beach house. It allowed me to go shirtless and carry my G26. I also shot IDPA with a guy who carried a snubby .38 in his and he was faster to draw than most others shooting the matches.

This- I agree 100%

I own a Smart Carry and the Thunderwear holster appears to be the same thing.  That style of holster is good to go!  It's a great holster to wear with sweatpants, gym shorts or any pants that don't use a belt.  Believe it or not, once you get used to it; it's not that bad.

No a lot.  I use a Smartcarry, and it's good to go as one of my deep carry options.

Where did you shoot this IDPA match? Smartcarry and Thunderwear are not allowed in any IDPA match, just like crossdraw, SOB or shoulder holsters.

To the OP, these holsters are deep concealment holsters which means they compromise ease of use for concealment. Just like ankle holsters and pocket carry they are slow to draw from and  can be impossible to use in certain positions like seated in a car. If you want one try it out but understand the compromises.

Gringop

If you don't have any pockets or a belt then ^^^^^^^^^^^^^^^^^

Here in AZ. It was club sponsored and not "true" IDPA rules.

I too have a SmartCarry for my G27. Like others that have weighed in here, this rig while not perfect for everyday situations has its applications. Sweat pants, light weight shorts, etc are how I use this rig as well. For me however, the back strap is not comfortable against bare skin and usually calls for a tucked in "wife beater" undershirt. This same strap has a tendency to rid up revealing itself in the back, above the waist line of whatever pants / shorts I am wearing.

Don't expect to run. Sitting down may require a little getting used to as well. IMO this rig provides more options for carry which is a good thing.

Gonna chime in here ... I've run a 5K with the SmartCarry and a G19 on.  YMMV.