You know, Spell Pierce is way less of a control hoser than Stone Rain.
this conversation bores me. i am hijacking this thread to start a discussion of "how many creatures do you have by proportion of spells" in your cube
mine: 207/377 ≈ 55.0%
typical grim mongolith cube: 48%-50%
discuss
spell pierce doesn't put your opponent back at least 1 turn of development for the rest of the game, or randomly mana screw your opponent out of nowhere.
even if the control player keeps hitting land drops, being a land down is going to stall their ability to play out their hand; while spell pierce destroys them harder for the particular spell getting pierced, stone rain effectively force spikes every spell they play for the rest of the game
it's misleading to say that stone rain costs 3 and thus costs the caster more tempo than spell pierce. leaving up U for more than a turn costs as much or more mana as just casting stone rain; wasted mana is just as real a cost as paying for spells.
The whole point of Stone Rain is to deny access to a colour, though. And if you're lucky, multiple colours. It's not about the delay, so much as the complete denial. Unlike with counterspells, where you're aiming to hit their best spell, but sometimes have to settle for any spell because you can't afford to hold up mana forever, Stone Rain always hits the land you're pointing at.
I mean, it's not really that effective against the mono-Forest deck. But against UWR, who's just finished searching up that Sacred Foundry to assemble ? Yep, that's got a giant bullseye on it. Who says we're allowing you to cast your Wrath of God next turn - let alone at all?
Denying access to color is the ideal scenario with land destruction sure, but it's not the whole point or even the primary point IMO simply because you can't rely on that outcome. Against a deck running two colors with a solid mana base, you do not have good odds of keeping them off the colors they need. Your odds obviously go up the more greedy they are with the splashes and what not though. Still, if that's what you are after you are going to end up disappointed with how well Stone Rain performs in your deck.
But delaying a control deck one turn of mana development while you continue to pound away with your 1 and 2 drop is often all you need to seal victory. That's really what Stone Rain and friends are best used for. It's a tempo play first and foremost.
I like Grindstone + Painted Servant in cube! I run it and it's always been fun: it doesn't come up too often but when someone assembles it, the whole room usually has a good laugh. I wouldn't run vault-key but painted stone can be disrupted by removal: doesn't seem too bad!