For many years I was content to just stroll into shul and take just about any siddur off the shelf and get started, but over the years it seems I've become more and more picky.
At one point I decided to get a pocket weekday siddur. It's great knowing you're always prepared, and if you really do keep it in your pocket, it doesn't make sense to carry around all the extra bulk of a complete siddur, where about half the pages are for prayers that come along once in a blue moon.
Recently a few publishers, such as Miller and Simchonim, came out with a smallish (I wouldn't call it "pocket size") soft-leather bound siddur for weekday Shacharit only, which is handy because you always keep it with your tallit and tefillin, and again, it doesn't take up too much space or add extra weight.
My son really likes having a pocket Shabbos siddur as well.
For many years, I was almost never the Chazan, but when my father passed away I suddenly found myself in the limelight as Chazan all the time. Since I'm not the type who feels especially at ease in front of a crowd, I need to be sure I'm not going to get confused during davening. So I started coming a minute or two earlier and carefully vetting the siddurim available to avoid the possibility of missing or torn pages, as well as siddurim that can leave room for confusion, such as those which combine Minchah and Maariv on the same page, which means you have to look a bit more carefully after Shmoneh Esreh to make sure you're saying the right Kaddish, etc.
After a few days of siddur selection, I decided it makes sense to buy a siddur that I like, so that the tefillah flows easily, without having to engage in technical tasks as I recite the prayers. And since I'm often the Chazan, it's important that the print is very clear and plenty large.
But it also occurred to me that making the tefillah flow easily, without having to look around the page, is beneficial even to those who do not step forward as Shaliach Tzibbur, but simply want to be focused on their davening.