From my perspective, I think 2
♠ is clear. I'd consider it mandatory, but, I can appreciate how others might differ.
While I do agree with Felicity that agreeing a fit is important, I don't really see this as one of those auctions. While rebidding spades doesn't
promise 6+
♠, it's highly suggestive of it. And, it's a guarantee if you ever agree clubs later if partner doesn't happen to support your spades. Knowing that you have 6
♠ might be the difference between a part score and game, or game and slam, in clubs.
So, while Mikeh would bid 3
♣ with only 5
♠ and a known 8+card fit in
♣, I think that changes when you actually have a truly rebiddable suit. And, this is about as rebiddable as a suit can get.
I'm not just willing, but
happy to play 4
♠ in a 6-1 fit over 3NT. There are so many ways that 3NT is going down when I have no entries to cash this spade suit. And, I will take a spade slam over a club slam every day of the week with this holding when partner has big values and 2 card support. It's not even close.
To illustrate the value of this hand, if partner had something like:
then this hand would be making slam on a spade finesse and a non-heart lead. And, that's not enough value for a reverse. And there's no reason to suppose that partner has a minimum when opponents are silent. It's clear to you that they have a stack of hearts, and they aren't bidding.
Why are spades maybe better than clubs? Because partner's club suit might be rather poor, AXXXX
♣ with some pretty solid diamonds for you to pitch your club losers on is still a good situation.
Sometimes clubs will be right, but, you don't lose the ability to agree clubs later. I disagree on this point, I think 5
♣ as your next bid clearly shows minimum-ish values and much better than suit preference over whatever partner bids.