I've been doing crossfit for 6 months now. I think our Crossfit gym might be more moderate than yours. I've heard of a few people throwing up at ours (as I'm sure some do at their weight rooms), but it doesn't sound as intense as yours. I've never felt that sick. Really winded and really challenged, but not to the point of puking. I used to go to the gym and do my circuit, socialize a little, and then leave. Like the guy above, I liked the predictability of it because I could control specific things. I did the Body for Life program several times and definitely saw major results from that. In Crossfit, I haven't seen the bigger bulky muscles that I got from weight lifting, like in Body for Life, But, Crossfit definitely has several great advantages for me:.
1.) My body overall is getting stronger, as a unit. I can tell that my core is stronger. Yes, I see gains in muscle size, but not like circuit training. This is ok for me because I'm built kind of big anyway (broad shoulders, etc.) Our Crossfit also has exercises called "Skills" that are basically like circuit training that you can do at the end of the WOD (Workout Of the Day, for those non-crossfitters reading this) that pair well with the WODs for that week. The Skills are designed to help you get bigger, stronger muscles for those Crossfitters that want to build more.
2.) I enjoy working out "functionally". The workout philosophy of Crossfit emphasizes functionality. Some weight lifting routines just don't transfer to the real world. When will you ever use your quads in the real world like you do in the Leg Extension machine? Never. Or use your chest in isolation like in dumbell flies? Not much. Because Crossfit emphasizes whole body, core, functional fitness, I feel like my body is becoming a better machine.
3.) Fun. While I loved the gains I made with just doing circuit training, I felt that I was missing something: Fun. I wanted the competitive surge I felt when I played racquetball. I wanted that adrenaline rush I get when I play dodge ball. But, how could I get it while I'm lifting weights? Crossfit gives me that. Also, every day is different. Almost like an adventure. Our Crossfit posts the WOD the night before, and I get a little giddy looking to see what it is. Here is tomorrow's WOD: after basic warming up and some basic lifting, ever minute do 5 burpees and then do as many thrusters (squats where you lift the weight above your shoulders at the top of the squat) as you can for the rest of the minute. Continue in this pattern until you've done 100 thrusters. The stale lifting routine is gone. Yes, I did like the predictability. I get some of that from the Skills (see #1) and can easily add in some basic weight lifting to target certain muscles.
4. Community. This is BIG. There is such a great vibe among the Crossfitters. There's something bonding about suffering together and then bragging about it. I love the team WODs. Every month we get new Crossfitters after they complete the Elements course. I welcome them like new family members.
5. Trainers. I read a lot on my own about weight lifting. I feel very informed about proper form. But, I've never had passionate trainers standing there supporting and yelling at me while I've been working out. I really like it. Our class sizes are limited to 12 people and there are usually 2 or 3 trainers present. The main lead trainer is always watching us and giving us tips and encouraging us. The other 2 or 3 are often adding their own support, as well. Plus, every Crossfitter becomes like a mini-trainer, helping you catch mistakes in form and cheering you on.
6. Bragging rights. I really liked the feeling I got when I could talk about going to the weight room to work out. I knew that I was doing something worthy, hard and respectable. With Crossfit, I get that feeling X 10. I almost feel like a superstar. "You do Crossfit? Wow!" Although I was happy for getting through my benching for the day in the weight room, it isn't the same feeling as getting through a 5-man team even in Crossfit. "I ran 2 miles while passing a 20 lb medicine ball back and forth between 4 other guys, AFTER I did 100 push ups, 100 situps, and 100 air-squats". It feels really great.
My whole approach to working out and fitness has changed. I love the challenge, I love the community, I love the "your body is a well-oiled machine" mentality.