With equal vulnerability, and a holding like (s) KQ9753 (h) K432 (d)xx (c) x, I would pass in first or second position, so that others can bid and I csn respond or overcall. I don't mind doing this with a weak but "near average" holding (8 hcps vs. 10). Partner figures to have 11 points on average, we could have "19," and a good part score, or even a game in either spades or hearts. My command of the major suits could make up for the slightly inferior point count.
But with a holding like (s) KQ9753 (h) 5432 (d) xx (c) xx, I would want to open with a quasi preemptive "weak" two because I don't have enough defense to stop an opposing slam on my own if partner has nothing. Also if I have four* high card points, and the remaining average around the table is "12," partner and I will have "16," leaving 24 for the opponents. And I consider my 5432 in hearts more like a Qxx than a four card holding.
Is it ok to open a "weak two" like I do if I feel I have "no" defense? (I would be "undecided" if my holding were (s) KQ9753 (h) Q432 (d) xx (c) xx.)
*I would open a "weak two" with as little as Axxxxxx, QJTxxx, or KQxxxx. This is a little weaker than KQxxxx (two out of the top three), but my rule is "one honor trick," that is, a six card suit headed by an A, KQ, or QJT, (but not KJ9, which has "holes" that can be finessed.) Goren considers QJT a "four" point holding.