Actually no. It's a bit more convoluted than that really.
Arcane is definitely the easier spec. By a lot. Once you get the hang of managing your mana, it's pretty easy to do good damage.
Fire is really only good for one boss fight in Firelands, and for that one fight it's ridiculously OP. Like, the logs on it for heroic are in the 150k area. Other than that, it's single target is mediocre. It's AoE is still pretty good, but there aren't that many situations in Firelands that really call for AoE. 3/7 bosses have AoE phases, but those phases are really short and none of those adds have a significant amount of health.
Frost requires A LOT of muscle memory to get the hang of. And it's AoE is very frustrating. I'm not sure how familiar you are with Firelands fights Digg, but there's a spider boss that has some AoE phases, and I can do really good dps on my mage if I can get to those adds before anyone else. Otherwise, my dps on that fight tanks fast. What's particularly frustrating, is that because of the way the Arcane mastery works, Arcane can actually do more damage with Blizzard than a Frost mage can, which is stupid. It really needs a buff in damage, and it'd be nice to have it either cost less mana, or be mobile. There are a decent amount of CD's to keep track of, and two different procs, which is what makes the spec rather difficult to master. That said, once Frost gets their hands on the t12 4 piece and are shatter capped, the rotation supposedly becomes much smoother and we do comparable dps to Arcane, provided the person knows Frost well and isn't ******** up.
TL;DR version: Arcane is greater than or equal to Frost, which is greater than Fire, except for one boss fight in Firelands, when Fire pwns everyone else out of the water. The problem is, Frost has such a bad reputation for PvE that there are significantly more mages that run Fire full time than run Frost.
What do you mean by ghosting though?