No. That's the honest answer to should I own both SPY and VOO, and I wish more articles led with it.
SPY vs VOO isn't a rivalry. Both track the S&P 500. Same 500 companies, same weights, same returns minus fees. The only durable difference is cost: 0.09% versus 0.03%. Owning both doesn't diversify you. It means part of your S&P 500 exposure costs three times the rest. That's not a strategy. That's an accident.
How do people end up here? Usually history. Bought SPY years ago, read that VOO is cheaper, bought VOO too, never cleaned up. Or two accounts with two different defaults. It's understandable. It's also fixable in one trade. In an IRA, just consolidate and move on. In a taxable account, mind the gains before you touch anything.
Don't take my word for it. Run an ETF overlap checker on the pair, or grab an ETF overlap analyzer app, iOS and Android both have them, and do it from the couch. You'll see essentially complete overlap, because there's nothing to overlap. It's the same portfolio twice.
If you want a second fund, buy something that actually differs. Small caps. International. Bonds. Duplication isn't diversification no matter how many tickers it wears. This is the whole argument for an ETF portfolio builder: decide the allocation first, then compare ETFs side by side to fill each slot exactly once. No duplicates allowed.
Same logic everywhere else, by the way. VOO plus IVV. QQQ plus QQQM. One index, one fund. That's the whole rule.
ETFCompare shows overlap and fees for every pair, so you can catch redundancies before they cost you. Start at etfcompare.fyi.