Read above. Good info.What kind of tone are you looking for?
If you want real clean tone go for the 300
If you like to use real tube overdrive and have some hair in your tone go for the 200
I use a 100 watt tube head and a pair of efficient 15's because I like to push my amp and use real overdrive. If I used a 300 watt head I would blow everyone out of the place.
I prefer a 100 or 200 watt tube amp. For the size of rooms I play they both work great.
If I were outside, 300 watts would be nice.