I was playing Winter Orb for a long time. Then I played against Loam-A-Tog in the Finnish Champs. Winter Orb came out and did nothing since I lacked threats. If it were B2B, I would've won that game anyways, since he didn't have enough basics to function at all under it. Basically, many decks stretch themselves too thin so Back to basics gives FS the tool to punish them for it. It's worse against Wombat, Rifter, etc. of course, but those decks are easier MUs anyways (not to mention, I haven't seen a single one in a tournament, online or off, for about a year), and it absolutely just kills the decks you want it against. It's also playable against X-colour Fish/Thresh, where X is 4 or higher. Basically, B2B feels more bomby than Winter Orb and gives me more time to topdeck if I'm having trouble finding threats or so. WOrb slows them down, considerably so, but B2B just kills them.
The Marco: It's all possible, but I wouldn't go about adding white spells to the deck; one Tundra is manageable as far as B2B goes, but I wouldn't want to rely on few Islands when it comes down. Specifically, taking out threats for answers is bad. One of the reasons I liked the new build in the first place is that I get to play 23 creatures, which is a lot more than ever, so I won't get creature fucked. Also, 12 of them draw in a way or another so I can chain creatures relatively easily. As for Engineered Explosives, it's a good card, but I don't think you really need or want multiples. There're MUs where it does very little (midrange decks starting at 3 or higher with their curve, mirror-like MUs, etc.) and I'd rather not see it in those, so I think 1 is the correct number in MD.

