Growth or value?

Value-oriented investments are at their cheapest levels in 30 years and trading at their biggest discount ever, according to a recent note by J.P. Morgan analysts.

But as growth continues to outperform value this year, they shouldn't bite just yet, some market watchers say.

"We could've had this story 10 years ago and talked about the 20-year anniversary of it being a bad market for value," Dave Nadig, managing director of ETF.com, said Friday on CNBC's "ETF Edge." "We could go another 10 years and it could be a bad market for value. I'm not sure that value and growth as an investing paradigm really makes that much sense anymore."

As of Friday's close, the iShares S&P 500 Growth ETF was outperforming the iShares S&P 500 Value ETF year to date, up more than 17% compared with its value-based counterpart's nearly 13% gain. The growth ETF's top holdings include the stocks of Microsoft, Amazon and Facebook, while the value ETF's biggest positions are in Apple and J.P. Morgan.

But even with the value ETF's 13% gain this year — not far off the 14% move — it's still not the time to buy into value, Datatrek Research co-founder Nick Colas said in the same "ETF Edge" interview.

"We tell clients, 'Look at value under two circumstances: one, if you're going into a recession, where you're looking for those staples stocks that are typically value stocks, and then [in] the first year of a recovery, when financials are outperforming,'" he said, adding that "financials are the biggest sector in the value group right now."

In addition, Colas said, more and more value companies appear to be under fire from high-growth players like Amazon, leading investors to flock to the winners over the ostensible losers.

"When you get growth, you get earnings leverage, and earnings leverage drives stocks, so that's a good thing," he said. "Value's been under fire for so long because that sector, those companies, are the ones under fire from technology and disruptive innovation."

And when it comes to a company like Apple, whose shares account for 7% of the S&P value ETF, the growth-versus-value paradigm really starts to break down, Nadig said, calling himself "skeptical" of value-based funds.

"I looked at some of these value funds the other day. The active risk of a big value fund [is] only about 8% if that active risk is coming from value," he said. "I think that we're in a world where these factors don't give you the kind of performance, the kind of risk adjustment, that you expect."