I have a several year old Thule Atlantis.
I went for a taller and skinnier one. With that, I can put a bike on either side of it on my B5.5 Passat wagon with OEM bars. Unfortunately, my Alltrack OEM rails are just a little short for that. In general, I don't think once can really recommend a size or shape. That is really all up to your needs. If you are in a Jetta Wagon, I don't think you'd ever have clearance issues. In my mind, the ultra slim ones are not all that useful, unless you are in a tall SUV and really need to get in to parkades or something.
Attachment method is important to me. I like quick and easy. I take it off when I'm done, and need to be able to move it between cars. Thule, Yakima, and a couple other big names keep it nice and simple and fairly adaptable to different roof bar styles and shapes. I know there are some cheap ones out there that still use some terrible fasteners. Something to be mindful of, I suppose. I also like that mine opens from both sides. I think I'd recommend that feature.
I'm also just a Thule fan in general as my last Thule box started having some issues with the clear coat after many years, and they didn't bat an eye. Just claimed it as a factory defect and replaced it with the latest model. I don't know if I just got lucky, but I found their warranty service to be great.