Best resistors for use in phono stage?

Wattage. What's the importance of this?

For your purpose—cartridge loading, the lowest wattage resistor will be WAY more than you need because very little power is passing through it.  You can use the lowest rated resistor you can find.

Larryi is right.

All components have sonic signatures. Whether a particular part is suited to a system can only be evaluated in situ.

Beware of FanBoy recommendations.

My opinions are based on solid state in a vinyl / ESL system. The Vishay VAR series are rated at 300 V if  IIRC, so they are suitable for any place in the amp (unless you are driving ESL's directly). IMO, VAR are better than any of the Caddock resistors that I tried: less edge, more clarity. Clearer than Mills WW.

@ieales  points out that all components have sonic signatures. That is absolutely correct. That certainly includes the resistors, capacitors, and transistors elsewhere in the chain. But this is a very good time to determine what you like, so that you can, in time, get more of it. I would definitely buy two Vishay VAR and two AudioNote to audition - that's how I started on the DIY road.

Good luck!