Brian,
Why not choose both.
I have been using Carrara and moved over to including LW 9,31. LW is a different approach to get used to and when you do, the options open up.
An add on to LW would be to get the LWCAD add on. it is really pretty impressive and if you do any arch viz work its is a real asset.
The other great point about LW is the plug ins and Lscripts. There are new ones fairly regularly and the list of existing ones is extensive. I have been collecting them as I go and using when needed.
Training can be very helpful. There are several good ones at kurvstudios.com and an organic modeling tut from thegnomonolgy.com site by taron. 2 1/2 hours of modeling and the guy uses about 5-6 tools in modelor. Cost is cheap at $25. Also check out at newtek.com for William Vaughn videos. They are all free to download and use. Covers alot of topics and can really help to learn the program.
I have seen you on MOI and 3D Coat. Andrew has several users that are LWers and moving files between LW and 3D Coat is improving all the time. There are improvements in 9.5 but NDA does not allow to talk about and it is not a production ready release for a few more months. It may help with OBJ imports from MOI.
The user forums at newtek are pretty good and do not forget the spinquad.com site, CG Talk and others that escape me at this moment.
A noticable trend has been for LW Character Animation folks to use XSI for the Char Animation and import back to LW for scenes, hard object modeling and rendering. Also 1 LW dongle can allow you to set up over 900 render nodes for render farm and includes screamer net to manage nodes. Incredible bonus to cut render times.
The render engines are opening up with the addition of KRay which some say will compete with Vray for quality. No flame me please as I am sharing information and learning as I go.
Brian, get all the tools that you can get. If someone offered XSI and LW, I would take them both and start working in each one of them for the softwares stengths. It seems very common for persons to have multiple software programs.
Beware of buying LW add on plugs until you know that it is needed for LW. There are many good ones and I know I recommended one (LWCAD) which I put off but glad I did because it is speeding up modeling with the snap tools.
Well, I hope to have added some info that may have been missed by others. Will I some day have C4D, time will tell. I am trying to keep up with the learning curve of each tool that I have purchased. I like the LW move from Carrara. It really has seemed to be a wise move even if the word vs icon approach is different and it is split into modelor and layout.
Best to you,
Joe
BTW... Did I mention Z Brush given a few renders I have seen o organic models....
better stop before the bank is broken altho it was almost half price at daz during march madness!