Not sure where the thought came from that you are moving from Southern California, it doesn't appear in your question. It would be helpful though, to know where you're coming from so that we can provide a more complete comparison, not just between cities, but also to where you live now.
I've lived in Houston, Northern and Southern California, and the midwest, in small and large cities. People diss Houston a lot, but that's typically from people who don't live there, or who moved elsewhere. Yes, it is relatively flat, sitting on ancient coastal plains, and it is further south and closer to the Gulf of Mexico, so it will also be hotter and more humid. It's a big city, 6th largest in the country, and is second only to New York City in the number of Fortune 500 headquarters. It has an international element, arts, entertainment, sports, and overall diversity of cultures and activities that is not available in Austin. This is not to diss Austin, it's just that Houston is big city, that offers things on par with other cities its size. Many, many people like it, and want what it has to offer.
Austin on the other hand, as many here have already commented on, is much more hilly, due to the Balcones Fault and the geological formations to the west, that create what we call the Hill Country. I do not believe it will ever come close to living in California, and while we like to think we have big city offerings, if you've lived in a big city, I think you'll quickly realize we are still a relatively small town, with somewhat of a small town feel. This too is preferred by many people, avoiding many of the big city headaches, although our traffic is probably on par with many of the traffic issues in Houston.
We have a strong offering of choices in education, including the nations 1st or 2nd largest university located downtown (we trade positions with Ohio State); we have a strong technology based job market (second to only a small handful of other cities); we are politically active on both sides of the aisle (Travis county is considered a bluish county in a red state); oddly, on a per capita basis, we have a very large urban population and vibrant downtown area that is growing rapidly; and our city government and police force have done an excellent job at curbing the undesirable element (much more so than almost any city our size). But we do lack the choices of activities of a city like Houston. We have no major league sports teams, we have a dearth of museums, and outside of a strong music focus, honestly, our arts and entertainment are simply not on par with a city the size of Houston. But, it's a tradeoff that many people are willing to make to get a smaller town feel.
Note, the city itself only recently passed 700K in population, but the areas population is considerably larger and very spread out (this is an advantage to keeping the small town feel, but plays havoc with traffic), with a large base of the 1.7+M total population located in Round Rock to the northeast (HQs to Dell), Cedar Park to the northwest, and a host of other small towns.
If your Trulia profile name is indicative of your career or passion, while I love Austin and wouldn't live anywhere else in Texas, I think you'll find more choices for this career/passion in Houston. If you want a smaller town feel, more connection to the folks around you, but with a growing offering in the arts and entertainment, along with a better overall outdoor experience, then Austin is your place to be.
Checkout Wikipedia for any city your considering to get a good overall perspective. Then visit both over an extended weekend, not to house hunt, but just to enjoy what each has to offer. Only then can you really make a more informed decision.
If I can help in any way, don't hesitate to contact me, even just for more perspective on each.