For me it was up, but by virtue of the surefit hosel. I was fitted at the National Fitting Centre for both the TS3 and the TSi3 (albeit 2 years apart, and my swing may have changed which needs to be factored in).
In the TS3 I was in a 10.5 head (played it at 10.5), in the TSi3 I’m in the 10 head (playing it at 11.5). The fitter could have got me at 10.75 obviously in the TSi3 with the hosel, which would have been broadly similar loft to the TS3, but he felt I needed more loft in the TSi3.

Thanks for the reply. I've heard conflicting results and I know it should go without saying that you have to get fitted to really know. I was trying to narrow down as much as possible and then try to conduct my own fitting at a local shop that lets you demo new on the monitor. $75 minimum to get a professional fitting just to see that my ball speed gained .5mph from the TS3 is what I'm trying to avoid....

Two things - ignore the past, go in with a fresh mind and trust your fitter whether they put you in 8* or 12* senior flex or extra stiff etc. you should be able to see why and if it is clearly better. Find a Titleist demo event in your area, they are free. Most places also allow free demo's and most fittings are free with purchase.

Ended up in a 10 degree. Fitter suggested it is better to Surefit myself down vs up.

Just a data point. Old TS3 8.5 degrees B1 Surefit hosel setting. At fitting went down 1/2" in driver shaft length which greatly decreased dispersion. Then added +4 grams in weight made it easier for me to find and square the head but also increased dynamic loft from printed static loft. Therefore new TSi3 8 degrees B1 Surefit hosel setting. Highly recommend to get fit.