IMO...

With high-end paints like this, the primers CAN SOMETIMES make a difference. With some of the FPE primers, they develope a little "harder"/denser/more impermeable surface, slightly increasing their topcoats' stunning gloss-development.

Am I saying you'll PERCEIVE a difference????
THAT'S "in the eye of the beholder"!

As long as you're using the good primers, you should be good.

HOWEVER >>>
If you're pretty fussy about exquisite trim appearance...ESPECIALLY with a S/G...
* Apply 2 coats of the BM primer about 3 hrs. apart.
* Wait a half-day, or maybe 'til next day, then evenly scuff-sand those primer-coats with ~ 180-220-grit paper.
* Remove every molecule of dust!!
* Now you've got the optimum base for gloss-development of your topcoats.

In any case, call F&B, or even FPE, and inquire about what makes their primer different! I know why (I gave you hints here...), but I want you to hear it from them!

* I've used a few FPE products.
* Haven't had the chance with F&B yet, other than matching a couple colors of their actual samples a customer brought in.
Neat stuff!

Faron