When it comes to the electricity itself, there is no difference at all. A cheap electric supply is the same electricity, it's simply provided by a new supplier (unless you opt for green energy - more on that here). As suppliers buy and generate different sets of energy they also have different prices. What's more, you might be on a tariff that is simply more expensive, such as a standard tariff. If you decide to switch electricity don't equate a lower price with worse service.
As an Exelon company, Constellation Energy is part of one of the biggest — and historically most polluting — corporations in North America. Given Exelon’s vast production energy, ranking on the PERI Toxic 100 list is perhaps not that surprising. The good news is that Exelon is upfront about its room for eco-friendly improvement and make it easy for Constellation customers to go green, too.