That +1 to hit probably factors in once or less a combat. With a warlord it might be more. Lack of hit points might factor in one in every 10 combats for him.
I don't buy this assessment. In my experience, if PCs start getting bloodied, the Leader(s) typically starts healing them (situation depending).
A PC who takes longer to get bloodied or does not get bloodied in an encounter really doesn't get any attention from the Leader until later in the encounter or even after a short rest. That "lack of hit point" damage would factor in nearly every encounter.
I cannot imagine that your group plays this much differently. It just doesn't make sense.
Sure, the BRV Fighter can still get bloodied. But, this has got to happen later in an encounter on average compared to an everything else the same FWT Fighter.
A few other posters have said BRV is clearly better. I fail to see how its clearly better for our party. Maybe some days a little better, some a little worse.
The math doesn't seem to support this POV.
One could have a party of 4 BRV Fighters and they would do just fine because they would rarely need a Leader. An occasional Second Wind or possibly a potion of healing would often do them just fine.
The same cannot be said of a party of 4 FWT Fighters.
But, the proof is in the pudding. Take two identical Fighters with CON 14 and with BRV and FWT being the only difference and run them through a dozen outnumbered by 2 on 1 encounters each and see who survives.