Ask for a quick demo. It depends on what your needs are. Some systems support computer cutters, some only specific types of cutters. If you plan on hand cutting only, it does not matter what software system is used. If you plan on using a computer cutter, you must use a service that uses a system compatible to that type of cutter.
Some systems are compatible to most computer cutters.
Of course, some software programs are more sophisticated than others and are capable of creating patterns with more accuracy and intricacy. If you have specific details you would like incorporated to your patterns, be sure to ask the service specifically what they are capable of doing. The more information the better. Patterns should be marked with all pertinent information. A sample of the garment is preferred.