I know you can’t pay for Pierce with delve, but with Cruise in the format it’s easier for these decks to play lands instead of sandbagging them to Brainstorm away. I think you’ll find in practice that it’s difficult to effectively Spell Pierce in the mirror.

That’s a fair counter-point. I may hate treasure cruise as a spell….but I do think your list is likely the best variation to take proper advantage of it. I also don’t know if Spell Pierce really gets “worse” with Treasure cruise so dominant…they can’t pay the Pierce cost by removing more cards and the deck still plays only 8 actual mana sources…so making them use up 1/4 of their potential mana base to not have their most critical spell get countered is still pretty solid. I do agree that Gitaxian Probe is somewhat questionable, so I like your 2/2 split on those two (though I’d be bold enough to go 3 pierce/1 probe).

It’s mostly the fact that Stifle takes spell slots and Waste takes land slots, and spell
slots are more valuable. I also value things like, as you said, blowing up Tabernacle\ Grove of the Burnwillows as much better than only hitting fetches.

The big emphasis is that waste proactively makes daze better, while stifle relies on leaving up mana that you may or may not use at a point in time when the deck is particularly hungry for sorcery speed mana.