Totally depends on the volume of reads and writes on the table, and how it is being used, size of database, performance of hardware etc.. If the database is heavy on reads a low percentage of available space means less pages to read when full table scans are performed, if heavy on writes then a lot of space available means less page splits so writes could be quicker.

Its almost a suck it and see as you have to monitor and adjust as required depending on your database use.

For small low use databases 90% is a good starting point, which is why the SQL Server 2000 maintenance plans defaulted to this.