The 1526 (and 1529) were discontinued for a while, but brought back to life by popular demand. The newer 1726E is physically larger and heavier, made to compete with the Kubota L2501, so without the 1500 series, Massey had a big gap in their model line up. Anyway, the 1526 is a great little tractor...most comparable to the Kubota B series. More flow and capacity than the GC1700 series, 3 range hydro, bigger tires with more ground clearance. Mid PTO to run a MMM, which you can't get until you go up to the 1700 premium series, which is way heavier than I would want running around my residential yard! I would says it's a tried-and-true design. Been around for while without any major known issues that I am aware of.
HOWEVER....at least on the Massey site, the MSRP for a 1526 is $1000 more than for a 1726E. So unless you really need that mid PTO, or really need a smaller machine, I would go with the 1726E.