Like JoAnne, I would choose CLEPs and DSSTs over TECEPs.
I took Psychology of Women TECEP because it seemed to be a relatively easy 3 credits and I had already studied a lot of Psychology material for other CLEPs. I took the paper based version because I took it at the TESC campus. It worked out better for me to do so. Here is the link to the online TECEPs
Thomas Edison State College - - Online Testing. I suppose they mean that they are computerized as opposed to paper based.
Besides being more expensive than CLEPs and DSSTs, they do not have the IC study guides for them. I made up my own study guide. Which is rather more time consuming and you do not have the feedback of the forum to help you.
I also took Art History TECEP which was necesary for my degree. There again I had no IC, IC forum or other convenient resources. I studied and studied for that one because it was a required course.
The TECEPs that I took were no harder than the CLEPs and DSSTs that I took. They have only 4 answer choices though and give you 2 hours to complete. You have to get 60 out of hundred answers correct, at least on the ones that I took. So the way that they grade them is different than CLEPs and DSST. Both times I received my scores within a week and a half.