The BT-T009 antenna looks interesting to me, but I had a few questions:
The datasheet lists the gain as simply “2 dBi”, is that an average/typical for all three bands or a minimum?
The product description says:
If you can handle the extra weight, the u-blox ANN-MB-00 or TOP106 will have better reception performance.
Those antennas only cover L1/L2 while the BT-T000 covers L1/L2/L5, does the increase in gain offset the loss of the L5 band?
If a UFO style fits your application, you cant go wrong with the SPK6618H :
That’s exactly what I use for my base station. 
One of the use-cases I was thinking about for the BT-T009 would be on my Jeep. I think it would mount really cleanly to the fiberglass top without me having to worry about a random branch causing too much damage when on a trail.
That’s likely the average gain across the 3 bands, I’d guess…hard to say without a graph :-/
The 2 more performant antennae listed integrate with a ground plane a bit better and have slightly higher gain…this is generally expected for helical vs non. Helical is usually better if using on a drone or similar where weight is #1…the MB-00 is probably even better for your use-case, with a mostly flat profile and uses a magnetic mount so it’d just move if it hits a branch rather than break.
Yes, the benefit outweighs the addition of L5 in this case, that’s why they put the note there 
And like suggested above if you’re after absolute precision the SPK6618H is #1