WW for me! I got really bored with Slimming World, yes you can eat unlimited amounts of certain foods but I found it oddly restrictive - there's only so many muller lights a girl can eat, even if they are free!
I found WW easier to fit into my day to day routine, yes you are restricted to your points but you learn how to stretch them and use them when you need them. For example I don't need a big breakfast, I would rather have a snack later at night, so I point for this accordingly. If you go over points one day you can save some the next day to get back on track, likewise if you've got an event coming up i.e. wedding, meal out, you can save your points and do more exercise to compensate in advance. Your points are based on height, weight, activity level and gender.
I also found the WW meetings more informed, they teach you about exercise, nutrition, reasons for overeating and techniques to avoid and so on, whereas SW seemed to be all about who had lost/not lost weight that week and you had to share this in the group - at WW it was up to you if you wanted to tell everyone what sort of week you had had. This is just my experience of each class though, others could be different.
It's completely personal preference though and what will fit best into your lifestyle, I know people who have done equally well on both, I'd look at their websites to get some sample meal plans, maybe give one a go for a week and see how you get on.
Don't worry about going to a meeting, take a deep breath and do it, to either one. The best tip I can give is go to weight in each week, without fail, even if you think you've gained, and stay for the meeting if you can. Good luck!