Without going into the cost analysis points-wise or economic 'bang for your buck' worth the infiltrators are my go-to in my lists.
The incursors are situational, and against mechanical units the haywire mines are useful, but for their initial abilities the infiltrators are my choice.
Pair up with the comms array and a phobos Lt you have a suitable unit capable of denying DS near your units, if deployed correctly- remember the rapid redeployment UM stratagem and stick the Lt with some eliminators in the backline so both squads will benefit from his wound reroll buff.
That is how I usually roll with them. Sure they can be an expensive unit when maxed out, but when played correctly do have their uses, now that scouts are classed as elite troops.