Having been trained to do manual flight plans in my first job I really think that computer plans are the only way to go.
Manual plogs OK for short sectors but fuel planning quickly becomes a pain in the ass for longer stuff.
Have used 2 systems in my time, AirData and SITA.
SITA is a keyword driven system, very good but quite expensive. As we were an adhoc charter airline it was ideal, simple to use and to create routes or join sections of existing routes. However understood from my boss that it was very expensive as you paid for each calculated plan.
Airdata is menu driven using routes created by each operator, no sharing, its OK and cheap as you pay for a year's use and can pull as many plans as you want. Very good for scheduled use as easy to set up for each day's flying. Major complaints are perceived lack of customer support at times and concerns over route data.