[Zelandakh]

 rmnka447, on 2016-May-05, 23:32, said:

Typically, these are either cheapest minor or cheapest suit. The only drawback is that sometimes you can't show a feature in the 2nd negative suit.

The traditional second negative after 2♣ - 2♦; 2M is 2NT and that still seems to me to hold up as well as the alternatives. It is more difficult after a 3m rebid, which is one (more) reason for treating minor suit hands differently from hands based on a major suit.

[Cyberyeti]

 Zelandakh, on 2016-May-06, 07:01, said:

The traditional second negative after 2♣ - 2♦; 2M is 2NT and that still seems to me to hold up as well as the alternatives. It is more difficult after a 3m rebid, which is one (more) reason for treating minor suit hands differently from hands based on a major suit.

It wrongsides 3N, using 3♣ with 2N showing clubs can be better.