There are several reasons that crits are more popular. First and foremost it is far easier to police and block off 4 streets in a 1/2 mile radius than it is to police and block off several miles in road race where the riders will often get strung out over several miles. Secondly, Crits can be used to generate business or focus on a particular area like a college or a downtown Lots easier to get a coffee shop to donate money or say okay to a race when the race will bring hundreds of spectators and riders across their doorstep. Three... crits are much better to watch from a participant standpoint the race goes by a particular point several times. Four, they are often more exciting from a pack sprint and/or accident perspective. Five, they are easier to officiate. You can easier place officials in places and pull lapped riders and such. It is hard to be everywhere at all times on a road course.
I like road races better, but if you want to cat up, youd better suit up and crit. It will help your pack skills, your speed, power, and cornering skills as well. Hop in... and for experience, in your first crit, just hop onto the back of the field in crit and stay to the outside on the turns, just to get a good view of how things work. Be wary, cause people usually slide out when they go down in a corner, but you will begin to see that. Experience, buddy. Then if you feel good, work your way up through the field and see how you do in a sprint finish. But, if you are stupid fast.. then just hang with the field and just pull away as the laps count down. Cat 5 races are interesting, but largely are not "slow", many are tentative so you see a lot of people popping off the back early, and you see many get pinched on the inside. There will be a fair share of wrecks, so dont bring your $4000 bike, or else you will leave crying. If it is wet... get ready... it will not be a fun event... road spray, wet corners, wrecks... oh yeah, baybee. Lastly, cat 5 races often do one of two things, stick together too well and are bunched and crazy, or they get really strung out... but most are accordian as cat 5 riders tend to cover absolutely everything. So, the stronger riders can pull away at the end cause the field is so tired from chasing the jackrabbits down repeatedly.
There are lots of races in St. Louis... if you dont mind the drive.
Just my 2 cents...