Personally, I think that too many people overcall. Meaning that we need a penalty double for it in bridge. But the modern fashion seems to be for "negative doubles" over overcalls. These seem to mean, "I don't like your suit, and I don't want to defend the opponents' suit, therefore I'm strong in the remaining two suits. At least relative to my 8-10 points. Meaning that it largely precludes the penalty double.
With some reluctance (and with certain partners), I used a double that means, I like the "remaining" major suit(s). (I hate minors.) It could be either negative or penalty, depending on the circumstances. Some examples:
1 Club (You) 1 Diamond (Opponent) Double (me). I like one, possibly both majors. Negative.
1 Heart (You) 2 Clubs (Opponent) Double (me). I wanted to bid one spade, but 2 clubs shut me out. Negative.
1 Heart (You) 1 Spade (Opponent) Double (me). I like one of the majors (and not yours, because I didn't raise, with Qxx or better). Penalty. (I have AKxxx or QjTxx and hope you'll pass me out.)
Should I stick to penalty doubles? Are negative doubles so compelling that I have to "switch?" Or is it possible to use a "blend" strategy like the one above?