tubs with or without grooves?

im building a rack and was wondering is i should buy tubs that have the grooves on the outside edges of the bottom like this one(will i have to set the thermostat higher cause of the gap between the bottom of the tub and the flexwatt)
http://i1138.photobucket.com/albums/...s/DSC00182.jpg
http://i1138.photobucket.com/albums/...s/DSC00186.jpg
or should i find tubs that are completely flat on the bottom

I have had both and it's really personal opinion. The groves help with run-off of urine, but are also harder to clean, you want to make sure nothing gets stuck in the recessed part.

sent from my EVO

Thats the same type of tube I use in my rack with flex watt heat tape with no problems.

I prefer flat bottom tubs such as iris because they sit closer to the heat tape Also Ive found that the grooved tubs put wear spots on the heat tape sliding the tubs over time

I've found that the grooves get pretty dirty, and have observed the wearing on heat tape as well. I just put an order for some Vision Tubs, I think you will find that they are perfectly designed for reptiles. They are smooth, well built, and priced well. http://www.visionproducts.us/htm7/tubs.html