HLG550 no doubt.
If you're into DIY, you can check my setup in my signature link, more bang for your buck.
Why in your opinion is the HLG550 a no brainer choice?
Unfortunately not a DIYer at all. So already decided to purchase a pre-ready unit.
One thing I dont like about the HLG 550 is that to move the driver outside of the tent i will need to do some wiring myself, whereas the new TS3000 already has extended cord to place the drivers outside of the tent for cooler temps. So this is a big plus for the TS3000 for me.
They seem to give off similar heat, both about 1600-1850 BTU, although again the TS3000 will run cooler for me as drivers can easily go out of the tent.
The HLG550 must be 22-32" distance from the plants.
The TS3000 must be 12-24" distance from the plants.
So I guess the HLG550 runs a bit hotter or higher intensity than the TS3000?
The HLG5550 pulls 480W at the wall.
The TS3000 pulls 450W at the wall.
Both seem to use a similar spectrum of light.
I attached a comparison of the PAR chart, albeit the HLG550 v2 chart is at lowest height of 22" and the TS3000 is at middle height of 18". So prob can add 20-35% to the numbers in the chart for the TS3000 to compare equivalent flowering height.
In conclusion they look like very similar units pretty much, except the HLG550 prob has a slightly better distribution of light across a 4x4 space.In fact where i am located they are both pretty much the same price. 
