Need Paladin/Cleric advice

As the title suggests, when building a cleric/paladin, is it better to go 18/2 or 17/3. I know the immunity to fear and disease aura's are pretty useful.
I'm building for Battle Cleric, obviously. So focus is on being scrappy and survival is the name of the game. Buffing & rez'ing & backup healing. Definitely not a healbot build.
So is it better to take the 3rd level of Paladin or stop at 2nd?
Thanks,
Aes

Edit: I should clarify. I currently have a level 20 cleric. He plays in a regular weekly group. He began as a battle cleric, then transitioned away from that to be more "clerical" I guess. Now the dynamic of our weekly group is changing, and I'd love to bring him back to being more of a battle cleric type, hopefully even a somewhat big hitter. So I'm going to reincarnate him and try something new; more of a semi-tank that buffs and heals, before/after battles, or in a pinch.
So, I've got it in my head to flavor him with some Paladin levels, possibly 3 Paladin levels, but maybe 2 if the benefits are greater. His role will be much more battle oriented, thus I'm thinking Paladin. I figure Paladin over Fighter because of the LoH, Auras, and the Immunities to fear & disease.
Does anybody have some handy advice one way or the other? I don't have the luxury of doing a true reincarnate and starting over at level 1, or I would; but rather I plan to keep him grouped with his current playgroup at 20+.

Thanks,
Aes

I went ahead and rebuilt my 20 Cleric as a Cleric/Paladin 17/3. What fun was had. So far he is very self sufficient. He works great in our party. And he can pull agro from the party Bard and our Sorcerer too. I haven't even gotten a good axe for him yet.

He's Dwarf and spec'd for PA & CL/GC. I'll post his build another time maybe, just to share.

Aes