Besides the obvious need to buy different ammo, frangible/NL seems to be TWICE the price per round

What is a 'best buy' in 223 and 9mm of this kind of ammo?

What effect will the different weights have?

What other considerations?

I would consider how important the class is vs. The extra cost.

I'm currently checking out the other locations the class operates in

Wut Range? Never heard of this in FL.

Ok, not sure of the range name itself, but Deep Woods USA is referenced in the class info.

Apparently the range operates within a national park.

I had to scramble for a class that required frangible ammo as well, was able to get some fiocchi. I think SG sells frangible 223

Frang ammo is indeed expensive and it sucks when we tell people that its needed for a course.  We generally point people toward Bite The Bullet out of NV as we have had good luck with their product over the years. One thing to watch is that with slower twist rifles, you may see key holing at room distances with frang since the twist rate has more to do with projectile length than sheer weight.

Its a requirement at Thunder Ranch and many shoot houses.

I have shot several thousand rounds of frangible in training over the past few years. This is the best stuff I have found:
https://www.sgammo.com/product/223-556mm-ammo/1000-rounds-556-x-45mm-50-grain-frangible-soft-point-federal-ammo-xm556nt1

The bullet looks like a soft point projectile, having a sold copper jacket filled with compressed copper instead of lead. I have found these to be superior to the Sinterfire and similar projectiles which do not have a traditional jacket as the bearing surface. The latter have a lot of reliability issues, including breaking on the feed ramps when chambering, and spontaneously decomposing as soon as they exit the muzzle from fast twist (1/7) barrels, leaving a shotgun pattern of tiny fragments on the target at ranges as close as 7 yards.