LM does give more damage, but the average damage on Lightning spells is less than the average damage of Fire spells, since Lightning has a much wider range of damage.
Lightning usually requires a significant investment in synergies to raise the average damage enough to compete with Fire skills, I'd say 50 points minimum in the Light tree to be Hell-effective, 60+ recommended. Of all the Sorc skills, FO is the least skillpoint-hungry, which is why it's the universal second-element skill for sorc builds.
The advantage of CL over FB is that it's tactically more useful, able to arc through immunes and self-target multiple monsters, whereas FB is "dumb-fire", has a smaller AoE, and can't penetrate fire immunes to hit non-immunes behind them.
It sounds like what you're headed towards is an Orb-it-aller, though with only 30 points you're not going to really have a Hell-viable fireball for your second element. It sounds like you might have overinvested in the Cold tree; you only really need to maximize one Cold attack and one other attack, ideally one timered and one non-timered spell. You also usually get less benefit the more you raise your Cold Mastery above -100% enemy cold resistance, for a generalist (ie non-boss-specific) sorc, after +skills, so most players will save their SPs and stop there.
Unlike when I made my cl/fo, there are now respecs. The only reason I wouldn't make one again, is because I'm usually using a sorc as a pure boss runner (FB/Meteor) or have all the gear I need to break most light immunes (infinity merc) so its a pure lite.
Depending on how you plan to use your sorc will really dictate your choices. If you plan on purely boss running, you can just stick to cold and fully synergize. Otherwise, I would probably go heavy on the lightning and use frozen orb out of the cold tree, along with some points in cold mastery.
Like I said before, FO is actually my favorite skill. Even though its timered, its area-of-effect is massive. But ever since I started spending the majority of time in Hell difficulty, I have gotten used to lite, although I still am not fond of it.
I'm really not fond of the meteorb build (which is really fireball/FO) because I like CL better and I typically see more fire/cold immunes than I do cold/lightning. Fireball is great against single targets, but CL goes through so many while only having to aim for one.
So I respecced to try out Chain Lightning / FO build yesterday, I got like 30 points in Cold and the rest in Lightning. Then I tried to help a friend with Hell act 4 quests, and immediatly noticed that my damaged is too low to do a more than 1 player game. 10 minutes later I respected again, back to fully synergized blizzard build. I saved like 15 points on Lightning tree though, just to make it easier for normal/ nm rushes. I do like 4100 blizzard damage with -150%ish enemy cold resisteence, and about 2 ~ 1100 CL damage. I think I'll stick with this build for some time.
My pure lite hits between over 42-44k max if I really fill her up on charms, and if I went for pure damage she could hit even higher, but I like the 200fcr. CL is around 14k or so.
If you're light is doing too little damage, you probably needed to switch to regular lightning, which you should have had points in as it does synergize CL. It only shoots straight, but pierces through just about anything.
Short of a pure lite sorc with Infinity merc, I wouldn't recommend rushing Hell, but depending on what quests and gear you have, its still doable.
By dropping FO and resorting back to a synergized blizzard, your CL is just shy of worthless in Hell, though its more than adequate in Norm/NM. I strongly recommend reconsidering your current setup unless you plan on avoiding cold immunes - for boss hunting, you're still find for Hell meph/andy.
What was your gear as CL/FO? Lightning tree really needs some +skills to shine. Full Tal's + Spirit is always your first priority after Insight merc, and once you get that you should see vast improvement in your CL efficacy.
You should hit 1100 max on CL just from 20 pts CL, 20 Mastery, and 1 synergy with absolutely no +skills from gear. Thats too few SPs invested in the tree, and too few +skillpoints from gear.
Even what I would consider a "bare bones minimum" CL/FO at only L75 should be able to reach over double what you're reporting
To me the choice between FB and CL (assuming you go with FO) depends on where you want to run and how much FCR/skills you can afford. Due to its autohit mechanics CL will outperform ball for large area clears, but will probably be somewhat underpowered for single targets like bosses when compared to fire. Also if you want to run keys you most likely want to go light as the countess is always cold/fire immune, unless you only target nihl who is normally not immune to anything except occasionally light. On the other hand light is a bit more mana hungry and requires a tad bit more fcr, so if you're wearing for example full tal's but can't lift a monarch you won't hit the bp. Again, to me the choice really depends on purpose, and you adjust gear accordingly. So fire if you plan on hitting bosses mostly (though at that point you're almost just better off with full blizz), and light if you prefer versatility and keys. With infinity it would be an easy decision :P
To the op, I have an 85 to 25 pt split with my sorc. She is pure blizzard with fb/meteor as a backup... I maxed ice bolt, ice blast, blizzard. Have 10 pts in glacial and 7 pts. In cold mastery after abot +8 to 12 + skills I do about 4-4.5k blizz dmg I put 1 pt into warmth firebolt fireball blaze inferno fire wall and meteor then 1 pt into fire mastery. With + skills this gave me a meteor of roughly 800 to 1200 dmg and fireball between 200 and 400 ... I jus started putting more points into meteor since its more cost effective dmg wise to put it in meteor which synergizes fire ball then fireball itself... I do now about 1.5k to 2k meteor and close to 500 fireball ... you can choose to spend only 8 hard pts in fire and finish cold mast or glacial spike or spend those pts on meteor..... sorry this is long on cellphone... also my dmgs are off the top of my head, perfectionists beware......