In my experience, the two paladin builds work fine, but you can't merge them. Doing so is awkward, and generates very little gain except a wider breadth of choosable powers. And with books like Divine Power, the breadth of choosable powers is expected to expand anyways. The strength paladin works just fine, other than the lack of power choices at 9, and a general scarcity of options, something that will hopefully change this month. Its on structural disadvantage is a lower damage divine challenge (starting at 3 or so damage instead of 7 or so), but I feel that this is made up for by far superior charges and opportunity attacks.
Just don't try to mix the two. No point to it.
Just don't try to mix the two. No point to it.