P90's will most likely be fine for playing blues, as a number of famous artists in the past and present have used P90's for this style.
I personally have not played P90s since I use a strat, but it's important to know that P90's are also technically single coil pickups but constructed a little differently and with more copper wires, providing a thicker, fatter sound overall. P90's can turn into a mushy sound if cranked up too high, but as with any type of gear, you may want to experiment with some settings before you find what you're looking for.
Single coils are a bit clearer than P90s but with the help of amp/effects, you can still give them a bit of a boost if you want it to sound a bit bigger than they are. I believe single coils provide the most versatility in the long run. If you're thinking about getting another guitar, you can't go wrong with an HSS strat.
The HSS will give you one humbucker, which provides a thick sound that you might want from a P90 but without the hum, and the option of cleaning up with the single coils.
That's my 2 cents!