it will also depends on if you're amp is for driving speakers or headphones.
When driving speakers with larger amps, you need to separate out as the other replies did in 3 stages
1. power supply
2. signal stage
3. power stage
In power supply stage, tube will typically have a more stable operational characteristics which give a lusher sound. However good transistor power stage can give a much better instant power or current draw which is critical to have the bigger dynamic range with a quicker sound without muddying the sound stage
For signal stage, a good tube signal stage like the re-issued McIntosh series gives a good warm sound and has a great harmonic ring to the tone. However, with digital musical and greater dynamic range and finer details, sometimes you may actually wanted that little extra zing in some transistor design to balance out the output stage
For output stage, usually more tubes the bigger the power as mentioned. Not always the case though. Some tubes like 211 single tube can give more than enough power to play with. Also it matters if it's single ended or push-pull. Single ended tend to have sweeter sounding and lush mids and usually have fewer tubes and thus single ended. But when you use something that's power hungry then you'll typically need to have push-pull design which almost by default double the tube number. It'll definitely give your more authority and power but when overly done, you'll loose the actual sweetness of the sound.
Then when talking about tube power, it also matter to have transformer or not (OTL). Output transformer matches speakers easily but at the same time can introduce it's own sound to the over all system regardless of some of the tube used. But with OTL which means output transformer less, it'll sound open and fast like transistor amps, but 1 little mistakes, the whole amp is fried and has the reputation of not being stable.
So in short, does more tube means better? For one thing, more tube means more expensive in most cases but not necessary better.