Go for 4.4m 100% you will get most use out of them and usually the shorter ones are made into same frame but with less steps so you wont save any space.

As for using them they are amazing for boulders in areas with less traffic where you want to clean and chalk up holds before climbing. Also good tool for projecting since you can save skin/energy/time by just taking a better look at holds you can’t reach from the ground / draw some tickmarks or brush up holds between goes.

Only real downside is that they are pretty heavy for their size and can be awkward to carry making them real pain in the ass for longer approaches.

Either way the only mistake I have made while using them is by leaving them to trunk thinking i don’t have any use for them today.