Well, you really have to think about what is of most importance to you. Do you care more about the connections you currently have in Houston or do you prefer to expand into a new city? How financially feasible would it be for you to move to Austin? Do you feel prepared to live on your own in a new city?
You can always build new connections in Austin. Several individuals applying to the MSW program are not from Austin either so they too will be eager to network and make new professional connections. Yes, you will have to network again. But, you will be able to build your network in Austin on top of the network you already hold in Houston. The one point that is the most difficult is finding affordable housing. You need to think about your current financial situation and see if it is possible to live in Austin. You may need to apply for financial aid, grants, and so on. You could find a place farther in north campus (typically cheaper) or live with roommates that are within your program or you know personally.
I would see this as a possible pitfall as well. It is up to you if you feel that this will stunt your growth. We cannot decide this for you. If you feel that you may live within the Houston area for the rest of your life, it may benefit you to continue to build your connections in Houston.
It seems that you want to go for something new but you are comfortable in Houston. That is perfectly fine. They are both great schools with phenomenal programs. Should you choose to go to Austin, you need figure out if you will be able to handle the change mentally and financially (and if you are up for the challenge). To add to this you need to think about what you want to be able to do past your MSW program.