Having owned a 1997 Divi 600 and now a 1990 pre-divi xj600 (seca), the older bike (radian) is a far better bike. It has much more power above 5000 rpm and the power kicks in between 7000 and 9000 rpm. It's getting a bit old now but I wouldn't swap it for the later bike.
Having said that, it's not like the power band on a RD350!