Building your own isnt that cost effective any more.
There are 3 types and the best will depend on what type of bulb that you plan to run because different bulbs will burn differently on different ballasts
I know that you run SE and not DE, so I will be posting my experience with SE lamps only
You have;
Electronic
Standard magnetic (cap and coil)
HQI magnetic (cap, coil and ignitor)
Electronic..... Back in the day before reeflux lamps were available, I used to believe that electronic ballasts belonged in the garbage because they underdrive most lamps, but the coralvue electronics actually run the reeflux lamps very well! Bulbs like XMs or other bulbs are underdriven on an electronic when compared to running them on a standard or an HQI
Standard magnetic.... Old, but tried and true.. Will fire most single ended lamps nicely. If running Reeflux, expect the lamps to be much bluer than the advertised kalvin rating. Reeflux will also look dim (that goes with blue). XMs fire nice and bright on a standard ballast
HQI.. Will drive all bulbs nicely..The problem is the HQI will overdrive most of the lamps giving a shorter lifespan of those bulbs.
Corals.. Different corals will color differently under different lamps reguardless of PAR.. Some corals will look their best under a very crisp, very bright 10KK XM,, while other corals will do best under a 14KK...
I could keep going but the tread would become OT.
My choice would be an HQI ballast with reeflux 12KK (SE), but over my orange and purple monties, and over my pink stylos/serriatopora I would want XM 10KK (even if its only on a standard ballast)