Best, of the three main builds?

[Psiberzerker]

I really don't understand this line of reasoning. Why bother going through the process of either getting boots with the Muffle enchantment (which are few and far between, and requires you to join a faction unless you get super lucky and happen to find some in a shop, which is highly unlikely to actually happen), or casting Muffle all the time, and collecting ingredients to make invisibility potions with, or working your Illusion skill up high enough to get the spell and then casting that all the time. Seems to me that it's much easier to just sneak around a lot; by the time I'm at level 20 or so, I can sneak around undetected quite well, unless I run directly in front of someone. By level 40 I can run directly in front of someone. And I can do it without casting a spell or making potions.

Also, by "skill points" do you mean perks? If so, I usually only take the very first Stealth perk, and the Muffled Movement perk unless I'm already planning on joining the Thieves Guild or Dark Brotherhood and using their Muffle-enchanted boots (and depending on my build, I'll go up the right side, but those perks are unrelated to being detected while sneaking). All you really need to use are two perks. On the other hand, if you want to successfully use invisibility spells, you'll have to use at least four perks in the Illusion tree to get Silent Casting, and you also might want to go up the left side and use another three perks to get Expert Illusion, unless you're not planning on using any magic other than invisibility spells. True, you don't have to use any perks if you get Muffle-enchanted boots and make invisibility potions, but that method has the disadvantages I mentioned above, plus the fact that you can't have any other enchantments on your boots (without being oh-so-lucky to find a disenchantable item with Muffle, and get your Enchanting skill up to 100 and use a bunch of perks to be able to put two enchantments on one item), and you run the risk of running out of invisibility potions.

TL;DR Building up your sneak skill and using two perks in the sneak tree is a far easier way to get around undetected, and you can do it at earlier levels.

Illusion is a main Skill for the build, and therefore, heavily invested in. I Destroyed the Dark brotherhood for the Shrouded Shoes, not even all that much of a detour. The main problem with Sneak is it slows you down, and when Invisible once the Alarm is raised, the AI still gets some lucky shots off with Arrows where you used to be. You could Silent Roll, but that's a short sprint, uses Stamina, and requires quite an investment in Sneak just to get to. That's what I ment by Skill Points, you'll have to level Sneak without Backstabbing to add even more out of character experience, and raising your level by at least half. As a pure Mage (what this thread is all about) I designed this build to do it all with Magick, and as low level as possible, so I wound up not even needing most of the Perks up the middle, just Quiet Casting. The Muffle Spell is a great trainer for Illusion BTW, so you don't Have to grind it at all, until you get the Shrouded Shoes. Believe it, or not, Flame Atronachs handle the Dark Brotherhood just fine.

It's your build, do whatever you like. I'm just sharing my experience, choices, and why I made them. You don't Need Sneak, but if you're willing to make that much investment (Mostly in time to grind it up, I suggest Sneaking around under Karthspire without the Alduin's Wall quest active) go right ahead.

 

[Adventurer]

Anybody can say anything. Chose the class you like the best and you will do with it the best. Period.

 

[FullmetalHeart20]

I think mages. It takes some time, takes some effort, but in the end it pays off. Even if you don't have dragonflesh, you just need to stun lock the enemies that can one shot you. But seriously, with one spell you can get full armor. No weight, no spending a dozen skill points.