It works in some cases, but far from all. It would probably be a good approach to treat them as fixed phrases, and only adopt the ones you've already heard used by native Norwegians.
"Det er vanlig med to biler." = "It's common to have two cars."
"Det er hyggelig med besøk." = "It's nice to have visitors."
A version that's quite common, but translates differently, is "Det er godt med..." which can mean either that something is tasty or good for you, or that there is a good amount of it:
"Det er godt med plass her."
"There's plenty of space/room here." or "It's roomy here."
"Det er godt med kaffe om morgenen."
"Coffee [is/tastes/does (me)] good in the morning"
"å ha" is the infinitive, "to have".
"har" is the present tense, and translates to "have/has" or "is/are having".
So "å har" doesn't work, as it's mixing two tenses together.
Of course the Norwegian sentence above isn't the best for explaining this, as it's using another construction in place of the infinitive, but it could also be written like this:
"Det er viktig å ha god service."
"It's important to have good service."
Hehe, well, I think you got half the answer you were looking for regardless. :)
As for whether there is any reason to choose one over the other, I don't think there is much difference between the two. I would use "med" in this case, but only because it's a bit shorter and easier to say.