My thoughts on these two:

Mega Sceptile: Has more utility than you'd see at first glance. Lightningrod makes it essentially immune to paralysis. It also shuts down Volt Switch *cough*Rotom*cough* and ruins electric strategies. It works well with Gyarados and on Rain teams. That said, its six weaknesses do hurt, especially Ice and Fairy. Talonflame will still suck. Unless it gets a revamped movepool and the stats are allocated correctly, I don't see this thing making it past UU. It's just too risky to use in OU as it has too many things that can check/counter it. Still, it does have a shot, albeit a small one.

Mega Swampert: You thought Mega Sceptile had it bad? Mega Swampert is, I'm sorry to say, probably the worst of the Hoenn Starter Megas. I think that Mega Aggron proves that you need more than sheer bulk and a good typing to justify the use of a Mega Stone. In fact, I believe Mega Venusaur is currently the only defensive Mega in OU, and that can be attributed to its ability to recover health. As a defensive Pokemon, MPert would need Drain Punch to even compete, let alone thrive in this environment. Not to mention that, Rock aside, its resistances seem to be inferior to MSaur's. But then, what if MPert isn't meant to play defensively? Swift Swim suggests that it'll try to be an offensive wrecking ball. Maybe its Attack is where it gets the boost. Assuming its Speed stat doesn't change though, I think it'll be too slow to sweep effectively. What it really needs is a resurgence of Drizzle (and this seems unlikely as the most obvious way to do this is...with another Mega.) Basically, if Politoed ever gets a buff that allows it to be relevant in OU again, then MPert will truly be the underwater beast its trying to be. Otherwise, I don't see any reason to spend your Mega Slot on this over, say MStoise MGyara. UU is my prediction for this one too.

In UU, both of them can truly shine. In fact, I wouldn't be surprised if Sceptilite (?) got banned in that metagame.

Aesthetically, they are both pretty awesome looking and I like them both more or less equally (I'm leaning towards Sceptile though.) In-game, they'll both be very useful. Competitively, however, I feel a tad underwhelmed by them.

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