Juron

Well, most veteran pvp'lers would not recommend you energy, mainly for two things, the smashing damage and the animation time. Smashing damage will highly get resisted in pvp like most knockback effects. The animation time of energy spells are also fairly large, you have to raise your hands, aim and send your funny blue bolts out of them. I think its about 2-4 second cast, dunno you have to test it out. Ice however has the fastest cast animation of all tree. Ice blast, ice bolt and bitter ice blast all got a one second cast animation. Its by far superior, also slow effects are rarely resisted.

Ice/cold is far better than ice/kin in pvp. You have to remember that all your buff/debuffs acutally MUST hit, base accuary in pvp is 50%, against defenders, scrappers or just shielded targets its even less. Most people do recommend atleast 2 +acc so's in their attacks, as a kin you also have to slot almost all your secondary skills. If your buff misses, you have to recast it which is one attack less on the target. Siphon Power is almost useless, you have to stack it up 2-3 times until you notice a great damage benefit, so you also have to hit three times in a row. Siphon Speed is however a great skill if it hits. Fulcrum Shift is a godlike skill in pve, however in pvp you will never find a group of heros to use this skill on, so most people will use it against creeps near the battlefield, if you use it on creeps however the - dmg debuff is wasted.

Ice has the huge advantage, snow storm and benumb are toggle powers, they ALWAYS hit, they drain your end a little bit faster but who cares. In combination with infrigidate you make your enemies crawl into your direction, there is no need for siphon speed if you can just slow them down. With heat loss you have another awesome debuff in the cold tree.

It's ice/cold for single target elimination and
Fire/kin for aoe king.