Over black friday I picked up both to play with, $1600 for the HD-b 3000's and $850 for the Sig, haven't taken either out of the box but I used to have an HD-b 2000 so I expect little difference optically from those to the new leica's.
They both likely do different things better. The leica of course is going to have better glass, and the 3000 fixed some of my complaints about the older model such as adding a decimal yardage. One thing I never liked about the Leica was only having one gun per SD card, they are not exactly easy to change in the field or at the range should you want to. Easy to lose a card or get dirt places you don't want it. Unfortunately I think in general the rangefinder advancements have plateaued in everything but max range. The big $ companies have not really added anything significant for at least 5+ years aside distance.
The Sig by all accounts is a great unit for the $, tons of features, and they are pushing the market to more electronics and most importantly fully integrated systems that communicate which has been a long time coming. However, once again we see more proof of Sig's poor QC and their willingness to let a borderline defective product not only out the door, but stay on the market without a fix. The diopter issue is a perfect example, there's no way any sort of even limited testing would not have caught that problem, worse yet they've done nothing to fix it for months. So if they'll let something that obvious slide, you have to wonder about what games they'll play on internal components.