Looking for advise - sicarans and pteraxii

[Bouargh]

Hi, I am in search for some pieces of advise. I already get one unit of 5 pteraxii sterilizors and one unit of 5 sicarans infiltrators. I have one additinnal box for each waiting to be built. As for pteraxii I am quite decided to go for a new unit of 5 as these lads have such a wingspan that 10 will be impossible to hide if in a single unit. These chaps are as hard to hide than scourges, even if I use genuine GW scenery. My real doubt is about the sicarans. Better boost up at 10 or make a second unit? Or maybe even ruststalkers? Do they worth it at 5 men strong?

 

Thanx for any input.