So, last night the wife was out, the baby was asleep and I wasn't being killed with work (there are a lot of preconditions that need to be met nowadays for me to play Magic). I jumped into a BTT queue and first picked a Kiora's Follower over Fated Conflagulation, Nyxborn Traitor and Nyxborn Wolf.

I ended up with a very strong deck but P2p1 I open (and take) Elspeth. I already have Karametra's Favor then pick up an Opaline Unicorn but don't see any more fixing.

At the end of the draft I am clearly going 17/23 (lands spells)

Here are the 21 creatures/spells I am definitely playing:

Creatures (14)
Swordwise Centaur
2xKiora's Followers
Leafcrown Dryad
Deepwater Hypnotist
Agent of Horizons
Nimbus Naiad
Nessian Courser
Nylea's Emissary
Thassa's Emissary
Horizon Chimera
Staunch Hearted Warrior
Siren of the Fanged Coast
Horizon Scholar

Spells (7)
Karametra's Favor
Strutus Walk
2xFeral Invocation
Fade into Antiquity
Oracle's Insight (insane with Kiora's Follower)
Raised by Wolves (never got to cast this)

My choice is this - stay at which point I can pick from the following (I need 2)
2 x Aspect of Hydra
Karametra's Acolyte
Savage Surge
Warrior's Lesson

Or splash white, which means playing
Opaline Unicorn
Elspeth
But having to play 3 plains.

What do you do?

I think the splash is playable. Elspeth is a beast, and her ultimate ends games, if you can protect her.

Not with that deck. I generally don't splash for double-mana casting costs. You're basically making your mana base significantly worse to play one card when you have very difficult things to cast in the beginning of the game.

No splash for me. Your turn two plays are and twice . Just put in an Aspect and a Surge.

Elspeth pays for the draft, no need to get greedy playing her and losing prize packs.

This^.

I don't recall ever splashing for anything double mana. It just isn't worth it IMO.

And I love to splash too. I'll grab a unicorn late in pack two in case I open a bomb pick 3 or 4 next pack not in my color.

This is the key point. Your mana is rough enough as it is. I would probably play Warrior's Lesson though! No one ever blocks unless they have to.

The other key (meta) point is this: How good is your UG deck? It actually looks just OK to me. I have had terrible times with UG without at least a few voyage's end, griptide, or even time to feed. Your removal is fade to antiquity and combat tricks. You are weak to aggro and not really that great against control.

Sometimes, if your deck is marginal then splashing a third color is your best chance at winning packs - obviously you are just counting on getting lucky with mana. Not sure this deck is that bad... but if it was a single elim or I was not one of the best players in the pod, I might consider just going balls out. But that's your call on your (relative) skill level of the tourney you are entering.

For the splash, I'd drop the staunch hearted warrior and.... Wait. That's Kara's Acoylte, not Favor. NVM! If you had a second favor. Then I'd say drop the warrior, run two favors, unicorn, and elspeth. The double white would be swingable then. With only one favor, its questionable. I misread the Acoylte when I posted the first time.

It's all about variance. Do you want to play a consistent low variance deck with less power or a high variance deck with a lot of power.

This is why the forum is fascinating because there are numerous different views and opinions none of which are necessarily wrong.

As it happened I did splash for Elspeth although I never go to cast her (I only drew her twice, one time I won before getting to 6 land and the other time I didn't draw a plains but won anyway). If I was to do it again I would go down to 2 plains as I nearly always had a follower in play meaning that I could untap the plains that I had.

This turned into one of my more profitable drafts as the server crashed during the finals (which I'm fairly confident in saying I would have won) so I got to keep all the cards I drafted (which also included a Heroes Downfall in a weak pack with nothing much else), plus get all my boosters and tix refunded and I kept the rating points I had earned from the tournament (and the 3 pauper games I won while waiting for the rounds to start).

As somebody who once drafted the nuts UG deck and decided to splash for the Foil Elspeth I pulled, don't do it.

My answer is almost always "not to splash". I spent a few hours doing complicated math once suggesting that if you splash one reasonably-priced card that, if resolved, ALWAYS ends the game in your favor, the number of game wins you pick up from drawing that card, the fixing to play it, and landing it are scarcely more than the number of losses you pick up due to mana screw (if you use your mana base to splash) or dead cards (if you use nonland fixins). It was more, but it wasn't vastly more. and in real Magic, no card is as awesome as the theoretical "winrate to 100% if landed" turbobomb I used to make the math easier. Close, perhaps, but not quite there. And all the numbers were small enough that they might not even matter over a 3-4 round small tourney: the sample size of games is just not large enough. But then, maybe I'm just risk averse.