You're absolutely right, crystal sync is not the only way to go. Recording wild sound and dubbing dialogue in post is an option and I have seen some really excellent shorts done in this manner with great image and sound. However, if you plan on shooting anything of any length or with more than brief dialogue you will have more difficulties and spend more time and money trying to sync sound in post than you would shooting sync in the first place. Having worked as an editor of a dialogue intensive short (22 min) without sync sound, I can tell you that before it was finished I wished I had never agreed to do the project.
What camera you use really depends on what you plan on doing. Professional quality projects can be made with inexpensive or older equipment if you plan correctly and understand the limitations of your equipment. On the other hand, amateur projects can be made with expensive, new equipment if you don't know what you're doing.