First, make sure that the market you want will be available with the software you choose. Not all softwares access all markets. For example, if you want to trade more than Forex, Metatrader 4 will not be your best option because the platform only trades Forex.
Be sure the interface is friendly enough for you to use. Although the algorithm pulls the bulk of the load, you still want to be able to log on and manage your dashboard and make any adjustments if necessary.
Next, look into the programming language you will want to use. This is if you may want to make adjustments and try to take on an advantage in addition to the software. Some platforms only allow certain programming languages, so be sure if this is a route you want to take that you will be able to perform what is desired.
For one last bit of research notes, be sure to ask for charts and performance in backtesting. Charts can help shed light greater on how the software and algorithms will perform and have performed. Asking for this information will prove beneficial rather than following a program blindly.