Another SS immersion chiller question

I've already decided to go with SS instead of copper, so that's not the question this time. My question is I was going to go with 50' 1/2" from http://www.midwestsupplies.com/stai...ort-chiller-w-garden-hose-fittings-50-ft.html

Unfortunately they are out until March, and I'm being impatient. I found 1 3/8" 50' from http://www.nybrewsupply.com/products/wort-chiller-stainless-steel-immersion.php

I'm going to be doing 5gal big beers and 10gal normal beers in a 15gal keg, anyone with experience have an opinion on how the 1/8" diameter difference will impact my cooling time?

Did you ask them if they will build a 1/2" SS chiller. I notice that they sell 1/2" tubing, so worth a shot. Somewhere on HBT someone (Bobby M?) did a comparison of chiller dimensions vs cooling times.

I did and they said they can't at this point. I'll do a search.

I couldn't find a specific comparison, any one remember this post samc mentioned?