I don't think type and decision making speed have a correlation. I see what you're saying, but it might be a little of a confirmation bias in your observations, willing to give a pass to certain types for taking too long, namely, J doms. But, I think your observations are accurate in that Te doms are very regimented in their outlook and so can seem to be very quick at making decisions. But similar to your case, where if you don't have the Ni framework, you can't make quick use of your judging function, the same is the case with the T(e?) doms, who, if they don't have a system, have to use perception in order to construct a new system or regimen and then won't be as quick in making decisions. Just my thoughts...