Would it be better to go for Heavy smithing for the better weapons, or Light Smithing for the Armor? I am leaning towards the Heavy Smithing due to the fact that my lvl 42 warrior has a daedric bow that might as well be a sniper rifle...what did you other thieves do?

Heavy armour path up to Dragon. This gets you Daedric weapons and Dragonscale (light) armour for the least amount of points invested

It's good because you can craft the best items.Since find items like Deadric is rare.I recommend use light armor to shuffle your movement.
at smith you can go by Elven-Advanced armors-Arcane blacksmithing-Glass smithing-Dragon and probaly Deadric.

This. Finding light armor is easy enough, but the good weapons are a bit tougher. Of course as a thief you will get some really good gear soon enough.

I just started a character on smithing, didn't realize there was a difference like that (heavy/light smithing)? You can smith all your armor and weapons, or upgrade them, just different ways/equipment and material to do it. Am I missing something in the smithing department lol?

Dutch ^^, thanks, that was my plan.

Heavy side for the weapons. You'll still be able to craft the best armor when you get to dragon. Use the DB or Thief stuff till then.

actually, if you go up the light side of the tree, you can't get daedric armor. It doesn't go full circle, it stops at dragon...

It's worth mentioning that in another thread it was demonstrated that the dps on Glass and Daedric bows are very similar, because Glass bows fire more quickly. So, if you're only going to be an archer, the Light side actually makes sense. If you want daggers, go heavy.

If I am an assasin stealth type of character, is there any reason to add perks past arcane smithing? I do not really care about having the BEST weapons or anything. I like to spend lots of time obtaining those from drops or quests. I simply wish to upgrade my armor quality and weapons. But don't know if there is a reason to max smithing if all I want to do is make them higher quality. Could spend 100 skillpoints elsewhere?

Glass weaponry isn't much worse than Daedric, so it's not a significant loss. If you really want to min-max, going the Heavy Armor side for Daedric and getting Dragon would probably be best. But considering you can kill most enemies in the blink of an eye with glass daggers, using the double-power-attack, it doesn't really matter.

If you were going to go through Smithing really quickly, and wanted to wear Dragonscale, I guess the Heavy side would make more sense. If you're doing it gradually, it's nice to be able to upgrade your armor as you go. Also, my thief doesn't have enchanting. He is gradually assembling a set of Glass armor with cool enchantments. (This is as much for fun as anything.) I don't think enchanted Dragonscale drops much.

If you are going to raise Smithing all the way up, you will probably end up putting perks into the materials paths. Otherwise it is probably not worth the points. You don't have to go all the way up though. You can hit the armor cap with literally any type of armor if you do it right.

Light smithing is more in character, IMO.

I usually go with Light, both to save perks and for the fact that since I always fight while concealed, the difference between Glass and either Ebony or Daedric really isn't going to matter.

I have taken all the perks before, even though it's a waste- one of the character in question's cover identities was an itinerant Blacksmith, so he needed to be able to craft with all materials at will.

if you're playing pure thief, you'll do most (all) killing from stealth so armor is rather irrelevant. i had a level 46 stealth archer (sniper) with a light armor rating of 36. sneak at 70 you're pretty much invisible, sneak 100 you are invisible, except for dragons.

but if you are going with smithing, i would perk up heavy side then use dragon scale with ebony or daedric weapons.

This is correct. The points are better spent elsewhere- especially for a dagger user. Taking arcane smith will allow you to hit the caps on DB/TG/NG armor, and if you use daggers ad DB gloves, then all you need is a steel dagger. Bigger numbers won't make things more dead when everything is one-shotted.

"Best" is meaningless in armor past cap, and meaningless in weaponry when you can kill just as quickly.