There's a DoM sub-forum...?

You're changing your job because of quivers clipping? I guess that's a reason as any. Anyways, from what I know about SMNs -- which is not that much in the end, I'll give you that -- it seems that BLM would have the more straightforward rotation in the the sense that you basically use two different spells in fire, one to two in ice, and two different for transitioning between them. There's more to it than that, of course, but that's the basic gist of it. It's also very error-prone and you can easily screw yourself over if you're not used to the timers you have to manage which, by the way, should get more lenient come next patch. At least Enochianless DPS is not horrible tier, but still drops noticeably. Any movement can and probably will kill BLM DPS, if you're not used to the fight

SMN, I believe, has more min-maxing than BLM and their opener is quite complicated from what I've heard, but you shouldn't need to worry too mcuh about that, if you're not interested in the end game raids, and I don't think you can do too much wrong with the Dreadwyrm Trance as long as you don't blow Deahtflare immediately. Pet management is also a thing, but they can work pretty autonomously, which is good enough for dungeons -- unless it's a Garuda throwing mobs around. Please don't do that. I don't even know what knockback works on nowadays, though.

BLM staves tend to clip through benches and big hats.

I think it's more about the playstyle in the end. Do you like watching your dot timers and managing your pet while doing constant small stream of numbers, or do you want to keep an eye out for self buffs and making sure they don't drop while getting big hits in? Someone who actually plays Summoner can chime in more, and the BLM explanation was pretty bare bones.