Hey, Ron, welcome to the forum! Based on personal experience, the first one I'd toss from your 3 is the RWS 350. It's what is called a long stroke or magnum springer, and they can be a real bear to shoot well and consistently, especially for someone new to springers. The 48/52 (same guns, just nicer wood on the 52) are also considered magnums, but are also quite a bit heavier, which helps tame them down some. It's also a fixed barrel, which may net you a bit better accuracy. But being relatively heavy, they may not be much fun to pack around all day. Supposed to be good off the bench, though.
Which brings us to the R9. Both the RWS guns have the TO5 trigger, which IMO, isn't that great. You can either adjust it to be short and heavy, or long and light, there's only one adjusting screw. Plus, the trigger is plastic, not a big deal, but even Gamo uses metal triggers :-). The Rekord used in the Beemans is nothing short of awesome, until I got my Air Arms S400, I was pretty sure it was the best trigger ever used on an air rifle. The R9 is close to legendary, but like just about everything these days, QC has slipped a bit. Still, they are one of those rifles that almost no one regrets buying. I've heard they can be hold sensitive, but most springers are. If this is your first air rifle, I'd definitely put the R9 at the top of the list, with the 350 not on it, and the 48/52 a not too close second. Just to be clear, of your list, I've only owned a 350, the others I'm basing on info from people I trust. One question, have you considered buying a used rifle? The vast majority of air gun guys take very good care of their guns, and sometimes buying used can be a real bargain. Hope that helps, and keep us posted on your choice. Later.
Dave