They are very similar I find, in difficulty and quality and other areas... perhaps you should go to the IF archive, or the IF annual competition results, play a few of the better games made with both systems, and decide which has the nicer feel to you. Â I personally prefer Inform, but just a bit. Â Then download the programs, and the manuals and get reading.
I'd avoid making anything in something that isn't tads or inform, because people that play IF will have the interpreters for those, other engines are much less popular.