[Free]

In a more standard approach, 1NT typically shows a weaker hand than Dbl. But if you're going to play sandwich NT, you might as well distinguish in length and strength of the suits instead of general strength of the hand.

In 2 partnerships I play 2 completely different methods, and I'm actually quite happy with both of them. Only one of them uses sandwich NT:
Dbl = shows the non bid suits, equal length/strength
1NT = shows the non bid suits, lowest longer/better
2♣ = shows the non bid suits, highest longer/better
2♥ = natural
2NT = extreme hand with the non bid suits (55+)

If we have for example ♠65432 and ♦KQJT we consider this as equal strength, while ♠KQxxx ♦KQxx shows longer ♠.

[PhilKing]

With approximately 57 different ways of showing two suits, god forbid we should have a way of showing that one of them is clubs.

If one is prepared to give up a natural no trump, using it to show 5+♣ 4+OM makes a lot of sense. This would only apply versus a 2+ club or diamond suit, of course.

[1eyedjack]

Amesbury and Payne in their book TNT and Competitive Bidding recommended (as I recall) something along these lines:
X = 3-suiter short in opener
1N = 3-suiter short in responder (you could swap this with X if you want)
Cue bids, 2N - 2-suited in the other two suits, of progressively extreme shape.

The book is rather dated (20 years or so I expect by now), and I think probably written at a time when it was less flavour of the month to open on a 10 count and respond on 4.

Anyway, just throwing it into the mix. It does have some attractions in that it allows you additional hand types where you might actually wish to play in one of the opponents' suits.

[Winstonm]

There are so many ways to use these bids: 1C-P-1H then: 2C=4S/5D takeout, 2H-5S/4D takeout, double =4/4 takeout, and 1NT=5/5 takeout.

[aguahombre]

I believe the majority of posters like 1C-(P)-1H-(2H) to show a desire to play in 2H.