I only have space for a rotary line - it's better than nothing but a straight long line is best definitely. But having it on a pulley to raise it up when full is very useful (and to drop it down for those of a shorter stature to hang things is also very useful....as a short squat myself!).
I am also veering towards annual replacement of pegs, as DH cannot bring them in out of the weather....I have a bag for holding the pegs that can unclip and come indoors easily (or move to another arm/other end of long line), except DH just leaves it out.
I use a few Ikea socktopusses to hang socks, jcloths, etc that only need 1 peg. It can save space and also makes those things easier to grab when the rain starts. And can make it easier to sort as you hang out, and then pair up as you take in, if you have that inclination.
Hang anything like tshirts/tops, jumpers, hoodies etc from under the armpits and have half hanging over each side of the line. There is far less stretching and distorting out of shape if you do that compared with hanging from the waistband always.
Having a rotary line or a clothes horse to put outdoors can give extra options for delicate handwash only woollens etc, that come out very heavy but you don't want them to stretch - as you can hang them over a few lines/bars at once.
And if you have choices where to put it in the garden, think about the direction of the sun's journey over the course of the day, where the prevailing wind comes from, and what times of day you are most likely to be using it - if you hang before going to work in the morning but sit outdoors at night, try to position it to get good morning to afternoon sun - but if you hang in the evenings to stay out overnight (I know, MN hates it but it is very practical and they still get dry!), you might want to find the more evening sun spot. And having a good breeze over it is always useful for speedier drying and better softness to the end results - I ADORE fluffy towels which are line dried on a very windy day for their softness next time they are used!