[cencio]

has anyone made a study to understand if it is better to open with a 5 cards on a major suit or not ?

[Shugart23]

I can tell you I have recently made a decision to treat all 5332 hands as balanced after a pretty lengthy discussion here on BBO just in the last couple months, although I cannot find the thread now. This seemed to be the consensus, but maybe not overwhelmingly as I recall. Throwing the 5332 Heart hand into NT means the opponents cannot overcall 1S As part of that discussion, if you were 5M332 and weak and partner opened 1NT, should you transfer or pass came up. Someone ran some simulations and concluded that playing 2M is better than playing 1NT

[P_Marlowe]

If I understand it right, opening all 5332 with 1NT is now expert standard in North America.
It strengthens openers minor suit rebid, it is now 4+

You sometimes loose a 53 fit. Which may or may not play a role, which partial do you play,
investigation of a major suit slam may also get harder.
The later depends on your choosen puppet version, on the other hand, you descibed your shape,
which may be simplifying the investigation.

Pik your poison.

For whats it worth, I open with the major.

[Douglas43]

I usually bid 1NT when I have hearts, and usually bid 1♠ when I have spades. But I look at suit quality and the nature of my hand.

[AL78]

Unlike most on here I play weak NT which may make a difference, but I tend to open the major if it is good enough that I'm not embarassed to bid it again if partner responds 2m, so something like KQT9x as a minimum.

[smerriman]

With 5 hearts, you don't really have much choice. If you open 1♥, and partner responds 1♠, you're completely stuck for a bid, with 1nt and 2nt bids misrepresenting your strength.

With 5 spades, you can get away with it a bit more, since you can rebid 2♣ over a forcing 1nt. But I prefer the clarity of showing my strength and shape in 1 bid.