I have a "no specific theme" personal blog (ribbonfarm.com), and my name is not publicly well-known other than through my blog. I also own the domain for my name (venkateshrao.com), which is redirected to my personal blog, but I have stuck with a name other than my own.

So I am basically exactly described by this question. The advantages of going with "catchy title" as you call it (look at Al Ries "22 immutable laws of branding" for helping thinking up one), are as follows:

1. You avoid the perception of being self-absorbed and "look at me, look at me."
2. If your site isn't about anything in particular, people WILL look for a common thread, and if you use your name, they'll jump to the easiest conclusion that the common thread is YOU. You don't want this, because unless there is something very special about you, that makes your perspective uniquely valuable (for example, you are a cancer survivor or a former CEO), this is a deathly boring connecting theme.
3. You want room for a better gestalt theme to emerge as you write, that is more interesting than you personally are. So pick an intriguing name that doesn't really mean anything. It is an empty brand container that will fill up as you write. Over 3 years, "ribbonfarm" has come to mean "long posts, with a somewhat dark/dystopian view point" which isn't exactly my own personality. But if I'd used my name, the effort to stay consistent with the perceptions of my name in my personal life would have severely constrained the ability of my blog to find its own brand.
4. Not using your own name allows you to retain a certain amount of objectivity. Your blog will seem like a lump of clay to you rather than an extension of the inside of your own head.
5. If you want to stay unfocused and eclectic rather than going after a niche like all those boring probloggers recommend (and I recommend you do), make sure your unfocused name appeals to you personally from a right-brained perspective. You should get excited and ideas should come pouring out of your head when you ponder that name. Your own name is a very poor creativity catalyst. A different name will encourage you to look outwards rather than inwards. For me "ribbonfarm" was a very catalytic term that still gets the creative juices flowing for me. After 3 years, it is nowhere near mined out. On the other hand, when I think of my name, all that happens is that all my everyday anxieties and mundane concerns descend like a fog over me, arresting thought. You want your blog to represent an escape of sorts.
6. Yuck factor: this is probably just me, but I intensely dislike own-name-focused personal branding. It leaves a bad taste in my mouth. Even if item 1 weren't true, I still wouldn't want to do it. I just find blogs named after their authors to be disturbing. I own my name-domain primarily for SEO. Someday I may put a dry, resume-like thing there. The whole about.me culture annoys me. Nobody's intellectual life should center around themselves as the prime object of study (except possibly as a specimen of "human"). Narcissism is not attractive.

You should still get your personal name domain if you can, or something close, and redirect. If you later become famous, you can use that for a more personally-branded site that can be used in non self-absorbed ways.