After attending Walmart's (WMT) annual investor meeting, CFRA's Arun Sundaram is turning more constructive on the big-box retailer and less bullish on conventional retailers like Kroger (KR). Sundaram downgraded Kroger to a hold rating, citing concerns over the company's ability to keep up with Walmart's expected 4-5% top-line growth. He believes Kroger's shares are now fairly valued around $70 and notes that the stock has already had a strong run this year, outperforming Walmart and Costco (COST).