Stocks stretched to 2009 highs last week, but market experts remain divided over the sustainability of the rally and the pace of economic recovery. Despite Fed Chairman Ben Bernanke's pronouncement that last year's collapse of Lehman Brothers "sparked a deep global recession, from which we are only now beginning to emerge," the fledgling recovery's health and endurance continues to provoke sharp debate among economists and market strategists.

The terminology is now familiar to even the most economically unschooled reader: "Jobless recovery," "unsustainable rally," "cyclical upturn" and "V-shaped recovery" are the stuff of routine headlines, but the meaning and importance of new data and recent market surges reveals a significant split.

Bulls say we are headed back to growth, while bearish types credit the plethora of government stimulus programs for altering conditions to the point where investors don't know the difference between real growth and a federal spending bubble.

Yardeni Research chief economist Ed Yardeni, once one of the financial commentariat's more bullish voices, reckons it's somewhere in between. The cash for clunkers program helped auto and industrial production, and the $8,000 tax credit gave home buying a boost, but neither is a long-term solution. Still, Yardeni told clients Wednesday that stimulus has provided a spark. It won't be a blazing path to growth, but "real GDP growth won t peter out next year, though it should be lackluster around 2%."

"We ve managed to muddle along before, and we will probably do it again," he wrote Wednesday. "Besides, we always fret about the sustainability of recoveries, yet they usually do become self-sustaining and don t require any additional government stimulus programs. In other words, business cycle history suggests that Muddling Along is more likely than Petering Out, in my opinion."

The keenest observers point out that market behavior is linked to economic conditions, but not always in the manner small investors would expect. Gluskin Sheff chief economist and market strategist David Rosenberg looked at the market rally since its March lows, and doesn't see the small investor playing a major role. Never before has the S&P 500 rallied 60% from a low in so short a time frame as six months, he pointed out Thursday. Nor has the index rallied 60% during a period with 2.5 million job losses.

"So who s doing the buying?" he asked. "Very likely it is still a combination of program trading, short coverings and portfolio managers desperately trying to make up for last year s epic losses."

That's prompted professional investors bent on keeping their jobs and their hides to continue buying a broad range of rising stocks on momentum, with little option to hold out for fundamental indicators of growth. Barclays Capital quantitative strategist Matthew Rothman wrote Thursday that "we continue to believe that the current rally is largely a 'junk rally' with poor quality outperforming, leading the market higher."

Regardless of whether the recent economic upticks are sustainable, stronger-than-expected or weaker-than-they-look, investors face a stark choice. Satya Pradhuman,a quantitative strategist at Cirrus Research, thinks it's time to sell, as government-rooted stimulus has pushed the market ahead of the recovery, and on Tuesday, wryly noted that "history shows that such optimism portends a heightened risk of disappointment in the coming months and quarters."

But perhaps it's better to be profitable than right, Richard Ross, global technical strategist at Auerbach Grayson, wrote Thursday. "Markets around the world have extended their gains in the face of persistent skepticism and incredulity and appear poised to continue their run. While it may seem counterintuitive, my analysis suggests that the technical backdrop for stocks is actually improving even as prices move higher," he wrote. "The absence of any real selling pressure, lack of unbridled euphoria, recent rotation into higher-quality industrial names and healthy degree of skepticism is the signature of a market which wants to move higher."

In other words, this wave keeps rolling, but investors should watch out for a sudden break and rocky shoals.