Difficult question. Four experiences:
I have a Hiwatt DR201 (before that a Vox AC50 and an Orange AD200B) and I love it. It's very heavy, though, and sometimes sound engineers want me to play with quite a low volume on stage, so I can't use it as it's supposed to be used. Of course it's very heavy, big, it needs maintenance, ..
A local rental company has a nice SVT + 8x10 which is often used at local festivals and when I know it's there, I don't bring my own amp.
Because I can't play as loud as I want, the Hiwatt stays at home often and I used a very clean SS-amp for a while. Too clean, so I used the Tech21ny VT Bass, which is great. Af course not as dynamic as a real tube amp, but I like it soundwise.
In studio I used the 30W all tube Ashdown Litte Bastard. Hiwatt sounds at low volume. It's not powerfull enough to use on stage though. I reviewed it for the magazine and I concluded that it could be nice to have a small tube amp for studio recordings and a hybrid for live use...
With that in mind I'm trying an Ashdown 550 Spyder head at the moment. It's not thát light, but I can carry it with one hand and I even walked to our rehaersal space. Bass in one hand and amp in the other. A five minute walk, but the Hiwatt is only good for a five second walk.
The 550 has two tubes in the preamp and the SS power circuit of the ABM500. I don't think it are excuse tubes, as Rob calls it. (Rob is right though, in a lot of cases!) It sounds quite good and I can dial in clean sounds and a bit of an overdriven sound and I like it a lot. It's better than the average SS-amp, not as good as an SVT, Orange or Hiwatt, but it has a normal size, it's not to heavy, reliable... I think I will buy this amp, but I won't sell the Hiwatt. I will use it when the band will get a van:)
I do not think the Ashdown is perfect, but it's a good blend of both worlds and very practical and easy in use.