[firmit]

Normally, I use Multi+Muiderberg.
A friend suggested this preemptive bid in 3rd seat:
2♦ as both majors or preemptive in spades - or strong nt of course.

One of his arguments, was that with a w2 hearts, opps would normally find their potential spadefit anyways. Never tried it, but there have been times were a major oriented preemptive bid would be nice to have ... Any thoughts or comments?

[rbforster]

I'm not sure I understand - you'll still be using Muiderberg, but you're considering switching to this different 2♦ bid instead of Multi? I suppose it depends on what you're trying to do, but hands with 5/4+ majors are certainly more frequent than a weak-two style 6 card heart suit. In addition, sometimes you can preempt 3♥ with those hands (or bid 1♥ light in 3rd), so maybe having a "both majors" bid would cover more ground so to speak.

I'm less clear on whether this 2♦ or regular Multi would be more effective as a preempt (as opposed to merely more common)....

- your opponents have the benefit of 2♦ being almost forcing (especially if you include the strong NT), but that will be true of both.

- people will be more prepared for Multi than this "♠ or majors version", and hence more likely to have a decent defense

- you're likely to win the bidding at the two level regardless of which version you have, since if they have hearts and 2♦ has the spade hand you'll know to compete (or they might regret declaring 2♥).

- it will be more risky for the opps to bid a natural 2♥ over this 2♦ than multi since opener might only have a 4 card heart suit when he holds both majors and so the chance of walking into bad breaks is higher (although the breaks are less severe than when you bid 2♥ and it was the multi opener's suit).

Anyway, those are a few thoughts.

Edit: any reason your only thinking about using this in 3rd seat? Seems like it would be fine in 1st/2nd too, although you'd need to work out the constructive followups (2NT asking and responses, etc).

[Free]

I'd advise you to keep playing multi, but using 2♥ as a hand with both Majors (because indeed a ♥ preempt won't work that often). That's a lot harder to defend against.

Compare them:
2♦ multi vs both Majors or ♠:
Opps don't have a cuebid after the multi, while they have one after the 2-way bid with ♠. There's still some ambiguity however, so it's not plain easy.
2♥ both Majors vs Muiderberg:
It's relatively easy after a Muiderberg to find a good spot (and opps usually know 9 cards after 3 tricks), while after an opening with both Majors (and they only have 1 cuebid at 2-level) it's a lot harder! Usually they'll try to find 3NT, but it's pretty hard when only 1 low level cuebid is available.
2♠ Muiderberg:
The same