It depends entirely on how savvy your clients are. Do some work for a company that has an IP lawyer and you can see the difference. The way it usually works is that you grant them a non-exclusive perpetual license to the software but maintain ownership yourself. If they want ownership you charge an additional 20% on the total cost, or whatever. I recommend contractors having their own contracts drafted by a lawyer and not signing client-provided ones. Much easier to be fair that way.