which one is better? so far i`ve seen that soloing with a cleric is damn difficult at the beginning(The one good spell i had to rely upon was Animate Dead). Later you get very powerful, though still weaker than mage. I`m starting a solo druid, is it more difficult than soloing with a cleric?

I don't actually know since I never solo but I think that with the druid it would be easier early at the game and at the middle but it would betougher near the end.
Druids level up astoishingly quick untill level 13.Then it is quite a chore.However if you have ToB I'd say go for the druid!

Clerics get spells faster, also they can wear plate armour and use better weapons.

Better weapons?I don't think so (Crom Feyr excluded).
As for armor I think that the druid can wear the shadow dragonscale which is almost as good as a plate mail.Also druids have Ironskins!!!!!

because i have ToB, i will go for the druid.

If you solo a Cleric, play a Priest of Helm. You'll get the one ability which makes a Priest into a decent melee-tank: Seeking Sword. You'll also be immune to Unholy Blight and yet still able to Turn Undead into little foe-shaped chunky bits. Several free castings of True Sight does not hurt, either.

If you solo a Druid, play an Avenger or a Totemic Druid. As an Avenger, you can throw Lightning Bolts and Chromatic Orbs, and you can turn into a Sword Spider. This is my favorite form ever. You get 5 attacks, and you poison your foes. This *WILL* kill Trolls, and will disrupt spellcasters. You can stay this way for as long as you'd like, which makes it better than the Mage's Polymorph Self spell.

NOTE: "Single Weapon Style" counts towards your bear, wolf, baby wyvern and sword spider forms. "Two-Handed Weapon Style" counts towards your fire salamander form.

For Totemic Druids, you'll get some nice random summons called "Spirit Animals". They're immune to normal weapons but don't do magic weapon damage themselves. They'll get you through to where you can summon fire elementals, which are more immune and do magic weapon damage. Long term they're cannon fodder (eg: vs. dragons) but short term they turn many areas into walkthroughs.

Good luck!

-- Nifft