The answer kind of depends upon your overall strategy. Both of these funds are going to have a ton of overlap on the top side, as they will contain many of the magnificent 7 . Where they differ is that SCHG takes a more broader focus with around 230 holdings compared to QQQM's 100 (it is a NASDAQ 100 ETF).
It is not that SCHG doesn't rely on big tech. In fact, it has a heavier weighting towards them than QQQM does. It's just it diversifies the bottom end of the portfolio a bit more by adding smaller positions in a wider variety of companies.
If I were to pick one today, I would certainly buy SCHG. I like the makeup of the fund. That said, both great funds.