Gregg -
What you are asking is truly one thing that each of us must ponder somewhere along our path as a bass player. However, it must be mitigated by each individual's personal constraints and preferences (ie - color, size, weight, cost, tonal shaping capabilities, etc). Needless to say, and hinging on your own personal philosophy -the best we can each hope for is to be true to our opinion of what setup can best accomodate the 'ideal' sound for me? It's a lot like asking is a pre CBS fender a better instrument than an Alembic? Depending on who you ask - you'll get a different answer, and even for those that answer alike- their motives will likely be different.
If you are a purist, or are partial to the tonality of tubes, then you are halfway to your answer. If you are less of a purist, or are not as partial to the peculiar tonality of tubes, then you are likely to be more receptive to what solid state is capable of delivering. Then of course there is the option of the new hybrid amps that integrate a tube preamp section with a solid state power section.
I have no absolute truths that I can share with you because this is such a subjective issue. All I can say is find out what your budget is... that will set much of the purchasing stage for you. In my case, I don't particularly care for the tone of all tube drive sound... but I also don't care for a solid state only sound either - so following the logic of many recording studios these days that use all digital recording gear (outboard gear) with Militarty Spec Type A Tube circuitry in the signal path to compensate for the lack of warmth inherent in the original 'dry' signal, I have opted for a hybrid tube preamp/solid-state amp head (the Eden WT-800). It gives me what I would consider the 'best of both worlds' and the rest is ALL Alembic.
Also consider the portability of the unit(s) when making the decision.... for me that was a big factor. I have used all tube units before (Boogie - grew to hate it) and used all solid state units too (Trace Elliot - grew to hate that too). I changed basses, I changed rigs - and now not only am I happy for the first time ever, everyone that hears my rig can't believe my tone.
Best Of Luck!
~O~