Which do you prefer...

IR Heat bulbs or UTH on side with a thermostat?

I prefer an IR heat lamp with a dimmer over a heat mat. The IR heat lamps do a better job of getting heat into the enclosure. The heat mats only heat the glass to which they're attached. It's a matter of radiant heating vs. conductive heating and glass is not a very good thermal conductor. The IR lamps also allow for night viewing.

If you want to go with a heat mat, look into Flexwatt heat tape. It seems to be preferred among reptile keepers and a lot of scorpion keepers use it as well. There are several tutorials on the web describing how to combine it with thermostats.

Right on I use Flexwatt with hydrofarm digital thermostat for my pixies. I like my IR bulbs but was thinking of switching to flexwatt because they wont burn out like the bulbs do...

I used IR bulbs for a year before switching to heat mats and flexwatt because the bulbs kept burning out. Probably just me doing something wrong but I like using the heat mats and flexwatt because they are a lot more cost effective for me.

thanks for the tips guys, any body use the heat rope?

Or with the heat tape, on the side I want it above the substrate?

I use some of the heat cable on my large desert communals, I place it just above the substrate level and it keeps the temps at 30 degrees celsius.

FlexWatt is a good product, but be warned, unless properly hooked up it can be dangerous. There are rumbles around, mostly at herp shows, that FW tape is soon to be taken off the market (here in the US) due to tendency to start fires.
Personally my tanks, and snake enclosures are all heated with flexwatt.