Personally I would go with the atronach, and come to think of it it was you who got me going on the atronach sign lol!

I am currently playing a high elf atronach that has armorer, blade, block, heavy armor, destuction, illusion and restoration as majors.
I am loving it. It is a melee/mage hybrid of course. I raised alchemy up to about 30 in the first level or two and make a lot of magicka restore potions. I enjoy my adventures running though the great forest hunting "Magic Mushrooms". I especially laugh about the time I did it naked for some reason (I think weight?)

Also fyi if you mix bog beacon caps with withering moon from SI you get a restore magicka and shield potion in one.

Oh, and btw I use a leveling mod so I don't need to hear anyone harping about putting all 3 endurance skills as majors. With the mod I use it doesn't matter.

Here is my two cents on the subject

Atronarch: for me it is more useful for races that are normally magic oriented like Khajiit,Nord, and the occasionally Orc Shaman since your character will end up tanking in oblivion realms late game but early on you would wish to have the versatility of the apprentice sign but later on of course it is more useful since early in at least my play through you tend to rely on your weapons.

Apprentice; for me it is more useful on the already magic oriented race Altmer,Dunmer,Breton and the occasional female argonian it provides the versatility you need so that you don't die from running out of magika.

oh, another bonus of the atronach is that going out to hunt for magicka potion ingredients helps get you out into the wild and you discover new places and stuff. I discovered several places today while hunting mushrooms and flowers. So in that aspect I enjoy the game more now that I get out into the wilderness.

If I was to play a pure mage I would choose neither of those. I would go with the mage class, no downsides, and I could fortify and absorb magicka with enchantments and spells

If i remember right ALtmer slready have 100% weakness to magic so if u add apprentise you will be killed by every necromancer

I'm playing Apprentice with a Breton atm. Apprentice gives 100% weakness, but Breton 50% resist, so it is only 50% weakness I just don't like the fact that your mana isn't regenerated, because when you are doing a quest with only warriors (or rogues or ...) you will have to go trough the whole place without magic!