All biddings I think about end on north making a 4
♠ control forcing south to ask for keycards or to get decisions, since he is the only one with a
♥ control, his lack of the
♠J makes it imposible to bid 6
♠ sadly.
About wich contract is best, 6
♠ is better theorically because only fails on
♠5-1, or
♦3-0 with them being able to score a ruff (only 75% of 3-0), I don´t know the exact % of this, but its for sure better than the 50% of 6
♦.
In practice it can differ, weak opponents (or those who don´t have a good concept of you

) will tend to lead
♣ against 6
♦, while on 6
♠ lightner double can come (and even north may try 6NT there on some biddings!).
Still we have to consider those 2 IMPS advantage for playing in
♠, maybe important since the choice seems tight.
I know a way to find 6
♠ would the best contract on my bidding system... but after 2
♦ weak in majors opening there is no need of playing in
♠ to guard the
♥K