I have never heard of Del Sol . I can offer no opinion on it.
The quality of bikes you will find at a bike shop will generally be much better than what you will find at Walmart and similar big box stores (such bikes are often referred to on these forums as BSOs...Bicycle Shaped Objects). It all depends upon what your budget is and how often the bike is going to be ridden. Any bikes that you are thinking about buying should also be given test rides prior to purchase to see if they fit and should be carefully examined to see if they were assembled correctly. Places like Walmart are notorious for less than stellar bike assembly.