It depends on several variables. Either will/can work as long as you have the right conditions for which ever way way you go with.
How where they transplanted into the 10inch net pot? This includes what type of medium they are in before being transplanted into the net pots. Are they going from one medium into a different medium? This can influence your water level after transplanting and until your roots start to grow out into the new root space.
If you keep the water level lower, you can always hand water from the top to keep the upper area moist enough for the roots until your roots start growing.
A variable water level at this stage can better for root growth.
Submerged roots will tend to grow downward. The side branching of these roots is much less then root that have a variable water level. Roots with a stronger side/lateral branching would be better to fill out as much of your net pot as possible.
Originally Posted by Douglas.Curtis
What is your ability to cool the nutrient solution?
When you can reliably and constantly keep the solution between 65F and 69F, a "Roots-In" hydroponic system is ideal. The roots can be fully submerged, as previously mentioned, but the stem must stay dry. Aeration of the solution is also needed constantly.
You do want the root zone to be cooler then the air temps. Water temperature isn't always an issue where you "Have to" keep the water between 65F and 69F. That is another one of those variables that depends on your set-up and your other environmental variables.