Is stranded wire inferior to solid core wire in this situation?

[MiniMe4Eng]

I have to run 2x20A and 1x15A circuits on the outside of the house for like 9m (27') -that is RW90 in conduit.

I have been trying without success to find solid core wire (individual wires) cut by meter. I would have to buy a 300m spool. Even if I use the same color for all the wires and use tape to mark the ground/neutral and hot I am still under 100m.

From what I am seeing it would be maybe easier to get stranded core.
My plan is to get with exterior rated cable to inside of the house and there to connect using a junction box with NMD cables which will be easier to push pull through the finished ceiling (there is insulation there)

From what the vendors told me this wire is more popular because it is easier to pull but from what I am reading technically it is less performant.

Are there any major problems that I should be aware of when using stranded wire ?

 

[3DDave]

Corrosion would be the most likely problem and slightly more likely to have problems at terminations unless ferrules are used.

Any moisture that enters the wire at the ends or small punctures will wick, carrying any corrosives with it.

Stranded wire was used between the anchors for the power at my house and the breaker panel - I would get water dripping into the panel as it ran down those strands during heavy rains.