I was looking at a no4 mk1 and possibly a no4 mk11 and was told the difference was a pinned trigger. Can anyone help me out or is it a big deal?

One has the trigger attached to and pivoting on the triggerguard (the No4 Mk1), the other has the trigger attached directly to the action.

So would it be better then to get the mk11 as this seems to be more like modern guns.

I don't think it makes any practical difference and the only way to tell, other than the markings, is to take the gun apart.
Grizz

It makes no difference at at all, except that the parts relevant won't interchange. The theory is that on the MkI or I* changes in humidity will allow the woodwork to swell and so alter the relationship of the trigger to the sear.

You will also find some MkI and MkI* rifles converted after WWII to MkII configuration. These were then know as MkI/2 and MkI/3 from memory! In all cases the easy way to tell is to look at the bottom ironwork.

In addition to what has already been stated, the #4 mk2 was produced during peacetime. No wartime shortcuts or quotas to make. They are also usually in better condition since they were'nt drug over some battlefield somewhere. In my opinion the #4 mk2 are the best of the Enfields and the last. Get the mk2