I teach both with the aim being to use a sensible mix of both.
On longer legs - such as will be flown commercially or on a CPL test - a slavish adherence to one or'th other will not be the ideal.
By personal preference I prefer to use a % marker per waypoint and mentally or pre-plen % of leg time. With a little practice this become very accurate. It also works well when applied as a skill to fuel consumption.
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