I struggled with this decision 2 years ago, researched all available photochromatic lens goggles extensively and ultimately ended up purchasing both the Julbo photochromatic polarized and the Zeal SPPX product as well. I was drawn to the Julbo because it had the widest range of change with respect to the amount of visible light transmission ("VLT") it allows. On paper, the Julbo appears to work best on cloudy days when you want a low-light goggle while also darkening enough to be comfortable on the brightest days. Having written that, the Zeal also had a great (albeit slightly less wide) range of VLT.
As a preliminary matter, I should mention that the Julbo is a French product and at least 2 years ago was only available through a distributor in New York. The ordering process was a little cumbersome in that you could not just order the product from a website. I had to correspond with the distributor by email, who then shipped the product to me. The Zeals, on the other hand, are manufactured in Colorado and ordering was very easy. In fact, I had a question related to the range of VLT and after submitting it, the President of the company wrote me back with a detailed explanation. The customer service with the Zeals was top notch.
On my next ski trip to Aspen/Snowmass I tested each goggle as scientifically as I could. My first day, I used the Julbo. It was so nice not to have to carry 2 pair of goggles! They worked well, changing just as advertised as I moved from sunny slopes to the shadows near tree lines. At one point, the clouds rolled in and the goggles lightened significantly. They performed just as advertised. I should mention that the Julbos are somewhat narrow and are better for people with smaller faces. For me, they were so narrow that I ended up with a gap between the top of the goggle and the brim of my Smith Variant Brim helmet. A great feature of the Julbo is that it has a clip at the back of the strap which allows you to use it without a helmet, or to add in the included spacer strap to make it fit easily over a helmet. Overall, I had a great experience with the Julbo.
The next day, I used the Zeal SPPX. The first thing that I noticed was that the Zeal goggles are significantly larger. If you have a small face and wear a helmet, the helmet may push the goggle down on your nose a bit. However, the field of vision was SIGNIFICANTLY larger. I had a much wider field of vision, and really could not see any limitation from the goggles. I also found the goggles to have a crisper, clearer view. It may be that the significantly wider field of vision prejudiced my evaluation, but to me there was really no competition. The Julbos were good, but the Zeals were much better!
The third day, I took both sets of goggles out with me and switched back and forth throughout the day. This experience confirmed my previous conclusions.
So, I ended up giving the Julbos to my teenage Son who loves them. Last year, I bought the new Zeal Transcend with the GPS and related temperature, time, speed and vertical. While expensive at around $500, they were really fun to use on the slope and also in the evenings when reviewing my runs from the day on my computer, overlayed over Google Maps. I don't know what you have read about the Zeals, but can offer that I have been extremely pleased with mine. Between the Julbos and Zeals, I don't think there is any question the Zeals are significantly better from a lens and field of vision standpoint. If you have a small face, definitely opt for the Julbo product.