Best all around is Arcane. You get all the tools that Frost has albeit with a little less specialization. You get a beast instant cast and increased haste if spec'ed. This is an objective game granted but don't listen to the rogue on what spec is best, he hates arcane with a passion for a good reason. Picking frost will only give rogues a better chance at killing you since you'll have to cast your main attack.
Don't listen to the rogue? Or listen to the mage who has played frost all the way through from bc with Domhring and Judgejudy, with Private Parts etc, to the beginning of cata? 1.2 second frost bolts are extremely important, especially if used with a mouseover macro for multiple targets. Same with sheep. Coc snare+freeze is a game changer in addition to gaining pet freeze. Your nova is a great 3rd freeze. Or go class cannon, arcane barrage with 1 freeze which apparently has the same tools as going frost. So I've been told.
If you roll pugs, it's nearly impossible to play a frost mage on the side these days, especially horde, but you will be the better mage come premade time because you have learned to survive on your own. Normally frost is extremely dependent on the support of healer(s) several dps and a tank to draw away attention on defense. In a horde pug, expect to have 1 "tank" and 1 healer on D. This makes playing a frostmage unbelievably frustrating.
As far as rogue vs arcane; it is easier to kill an arcane mage than a frost mage. Why? They are based on sp, not stam, they have 1 freeze, slower casting on frostbolt. They will basically use 1 attack, arcane barrage. Yes their blink is pretty op, but that's what you save shadowstep for.
Tips on beating a rogue as frost:
As a frost mage if you get sapped and a rogue gets an opener on you, you don't stand much of a chance unless you pet freeze him/trinket/blink etc followed by a freeze, then he will use shadowstep, that's when your nova comes in handy since he will be behind you, through a series of frostbolts + fire blast he will possibly bust sprint, that is when CoC is #1 because he will be approaching you from the front.. and quickly at that.. + your freeze off CD, mixed with more frostbolts+blasts+missiles he should be pretty dead... A rogue will crutch on shadowstep and sprint to beat a mage who is efficient in CC.
The real point being made here: Frost mages have more CC and more stam, therefore they are harder to beat as a rogue.
Also, sadly CC doesn't look very good on battleground scoreboards =/ and that's what the majority of "twinks" are concerned about today.