Clem von Jones

I think there should only be two basic positions: upright like a dutch bike for flat urban areas or aero position for speed and climbing. The aero position can be aggressive like a professional racer or relaxed like a recreational rider. You have to decide which of the two basic positions you're going for. I think that initially the upright position seems attractive to new riders but over time they realize it isn't as comfortable as they imagined because most of your weight is on the saddle, and the mechanical efficiency isn't great, but now they're limited because of the bike they've chosen and type of bars the bike has. If you have an upright style bike but want to climb hills or mountains then the limitations of the bike become suddenly apparent. If you have an upright bike but live in Amsterdam then you're not likely to have any issues. You can increase the mechanical efficiency of an upright bike by increasing the reach to put you into a more aero position and by swapping the saddle to a narrower one so that more weight is transferred to the pedals. As you increase forward reach you also have to move the saddle backwards a corresponding amount.

There definitely a tipping point to the aero position, or a zone you should be in that corresponds to the strength of your core muscles. If you fall outside that zone by having your bars too low or too high you'll suddenly notice a lack of mechanical efficiency during long climbs for example. For professional racers the zone is lower and more forward and for weaker riders the zone is higher and a bit further backwards.