overall time to print will still be similar compared to a .4 noz.

I agree with you mostly, but I wouldnt say simmilar time even though it can be even slower. 0.6 nozzle can usually print much wider lines (again less details) and therefore much faster. It depends on settings and model ofc, but I go for bigger nozzle just to increase line width and layer height (to speed up print by a lot!).

Line width can also be changed. Depending on the nozzle shape, you can print 0.5-0.6 mm wide lines using 0.4 nozzle without ruining the quality (depends on the model ofc). There are some best practice values for nozzle size / line width / layer height ratios, but no one can stop you from experimenting.

To increase strength, its true you want wider lines, but there are many other important factors like filament type, print orientation, temperature, speed, etc.

In general, bigger nozzle gives lower resolution and faster print time. But dont forget thermal limit of your hotend (max flow). 0.8 nozzle might not provide higher speed compared to 0.6 if you are printing fast and hitting your hotend limit already. Swapping nozzles is quick and easy on most printers. They are cheap and I think everyone should try different nozzle sizes, dont take that freedom from yourself 😉. For example, you can reduce XY speeds and still print much faster with bigger nozzle. For real size helmets I wouldnt use nothing smaller than 0.6 mm just because of print time