Slam or bash?
 

Ogre SK... Does it matter if I use slam for both my 2H and my 1h weapon load outs?
Does one do less damage?

Just always use slam, and make sure you train bash when you get it. :)

That's what I had been doing but someone said bash does more damage?

Slam only does 1 point of damage, and misses often. Once you get the bash skill it uses that instead.

Sources:
http://wiki.project1999.com/Skill_Slam
And also, using slam all the time on large races with and without a bash skill.

It hasn't been updated since 2014 is that still accurate? I probably need to do my own testing but I haven't used a 1hander yet.

Slam uses bash skill to calculate to-hit, but I do not believe slam skills up the bash skill. So you'll want to skill up bash separately (using a sword+board to skill up). However, assuming bash skill is up to date, bash is usually superior due to the superior DPS that 2H have over 1H (for knights against targets with normal AC).

I skilled bash once and then used slam and bash has skilled up using slam. However I don't know if the damage is different assuming the shield does not add damage?

They do the same damage from my experience. Only use for bash instead of slam is if you get an illusion to lose the large race appearance. Like t won't let you use slam anymore if you have a chanter turn you into a wearwolf , so you would need a 1 handed and shield to use bash instead. Illusions aside, just use the slam button.

Use bash if youre using 1h/shield or epic, use slam if youre using a 2hander

It does. You don't need to wear a shield to train bash. Slam trains it fine.