There are so many threads like this, debating between frost zealots and tesladins.
You want the blunt truth? Here it is:
They're both awesome. From first hand experience, I can tell you personally that they're both awesome. You'll be happy with either. The upside to the Tesladin is that it's extremely easy to make variants using the Holy Shock synergy (Tesladin/Templar) and just load up on CB to make the low physical damage seem like its not a problem. Another upside to the Tesladin is that with his best end-game weapon, Crescent Moon Phase Blade (CMPB), he has -% enemies lightning resistance, ITD (not much, if any, need for AR), no repairs/ridiculously fast, and additional open wounds to name a few attributes. The downside is the non-consistant damage, since the minimum damage, regardless of shock level, is 1. However, the average overall damage will be, typically, slightly higher than the frost zealots, and the maximum is much higher than the frost zealot.
However, the frost zealot is a favorite because of 2 reasons: firstly, it gives a more defensive and safe standpoint, as you can slow your enemies over 50% over a huge range with just the aura pulses. Secondly, it's cold damage! Everyone loves cold damage. The downside to the frost zealot would be the lower potential damage, no easy variants (other than some vengeance/conviction, which can be done on the tesladin anyway), and typical AR problems. Most of the ideal end-game weapons for the frosty include weapons like Heavens Light, Astreons, and the 'Black' runeword, none of which provide ITD, the best -% enemies defense coming from heavens light (-33%), but all providing huge crushing blow benefits (33-40%). I, personally, had trouble finding a way to enhance AR without using enchant on a demon limb, and while avoiding the use of 2x Ravens, or 1-2x angelics with the ammy, since I had other plans for my rings/ammys. So unless you come accross a Jah to spare on the weapon, if you're truly that devoted to the build, there are potential AR problems. However, if you just throw on the angelics/ravens, and max zeal, you'll probably be okay.
I wouldn't know which to pick if I had to choose... but if I was on hardcore, I'd definitly pick a frosty... hands down. But I enjoy my Teslafister (The tesladin/templar hybrid build) just as much, if not more, than my frost zealot.
From a non-biased point of view, I'd say pick either, or an even better choice: try both! I find that the tesladin can be a little cheaper, and may be more fun to start with, but I definitly wouldn't pass down the chance to create your very own frosty. :thumbsup:
Good luck! I'm positive you'll love either one... or both!