Onderzeeboot
Ecstatic Orb
I like having a white walker as a control finisher, both Elspeth and Gideon perform that role well. It's just that Elspeth has been a little obnoxious in recent drafts and I haven't played with Gideon in a while either. I don't remember which is more obnoxious. I do think the Gideon card has some really badass flavor though, and I like that he can be picked off with simple spot removal. Then again, he's basically indestructible versus a red deck unless they go big.
They're both pretty much the same power level to me, not sure which is more fun to play with though.
I tried both, and Gideon was far worse (as in: far more obnoxious) than Elspeth, Sun's Champion. That said, I cut Elspeth as well in a recent update. White doesn't really need the planeswalkers to be interesting in my experience.