Thunderbolt V's PCI Capture Cards

I was wondering from those that have used both the Thunderbolt Capture boxes (such as the Blackmagic UltraStudio 3D) and PCI cards, if they have found any additional latency or issues on these compared to the PCI cards such as the Phoenix Duel SDI card either fitted within a Mac Pro or a Thunderbolt Chassis?

Are the Thunderbolt capture boxes a viable option moving forward or will the PCI cards still be the best route even if fitted within a Thunderbolt Chassis.

Similarly has anyone tried the Blackmagic UltraStudio SDI (USB 3) capture box with Catalyst and if so how did it fair?

I have used both the blackmagic Intensity Extreme and Ultrastudio Recorder thunderbolt boxes on the retina macbooks and haven't noticed any additional latency vs the blackmagic cards in the Mac Pro towers.

Unscientifically I'm getting 1-2 frames of latency into the system over HDMI/1080i60 on the thunderbolt devices, I have not directly tested HDSDI however I'd assume similar results