I would take L. Walker just because he is going to start and start fairly healthy. Thomas could miss close to half the year (I haven't heard any further news) If Thomas is only out a few weeks I would probably go with him but the way it looks I will take Walker over Thomas.
Walker will play the whole year, Thomas may not be back until late May. Plus, I think Walker showed rejuvenation when he got to St. Louis last year and I think he will continue to drink from the Fountain of Youth and have an excellent season.
They're both a big injury risk but this is a no brainer you definetaly go with Larry Walker here. His upside is way higher, if he stays healthy and gets 400+ AB's hitting in the 2 hole for the cards his numbers would be great!!! LW still can swing a mean stick!!! Health is his only issue.
If he gets 400+ AB's expect something like:
.294 avg .964 ops 31 hrs 102 rbis 106 runs