Strokes for folks! There really is no definitive answer.
The theory is that its straight for cutting below shoulder height and curved for cutting above shoulder height (which helps the saw stay on the branch).
In practice we all have our own preference as both straight and curved saws work well in both situations.
You definitely get some advantage from speed/effort of cutting with a curved saw, especially the GC series (due to its fast cutting tooth design). This however should not be the driving decision maker as the difference isn’t a deal breaker.
With a straight saw you can achieve a more accurate finishing cut (think natural target pruning) and it is great for putting in a delicate gob cut and/or back cut when the situation is a bit too sketchy for your top handle chainsaw.
Straight saws are also available with smaller teeth (GSM and GSF series saws) for an even smoother finish when pruning smaller diameter branches.
Helpful advice? Probably not! We all have our own preferred option based on experience.
My ideal scenario is, a GC270 or 300 for larger branches and a GSM240 for smaller diameter branches and fruit trees.