With the 4/6 hi mod, HIDs in the hi beams would be ok. Your only downside is going to be the 10 seconds of warmup time until full brightness.
The benefit I see with my LED hi beams is that they are instant on to full brightness and I can flash them without worrying about damaging a ballast or wearing out the electrodes in the HID bulb. Plus the lifespan of the LEDs are thousands of hours more than a HID bulb, but that is not a major concern since they are in the hi beams.
The beam pattern is better with HIDs in the hi beam reflector versus LEDs due to the design. You only have LED chips on each side of the post and do not get 360° of light like with a HID. Before doing the 6 hi mod, I noticed there were areas of the road not lit up due to the beam pattern of the LED headlight.
There are pros and cons to each, but without the 4/6 hi mod, I personally would not run HIDs in the hi beams.