I only have a bridge Blackout so I am not much help but HaGGuS has had both in his old Loomis and he preferred them to the 707's. I am sceptical about all the Blackout hype, I have the bridge blackout, 707's, a 707TW and 60-7 here are my observations.
First off I 18v my EMG's so this is a comparison of 18v 707, 60-7 and 9v 707TW, Bridge Blackout.
The Bridge Blackout is scooped compared to the others. It is the noisiest of the lot and it is either on or off, you may as well replace the volume knob with a kill switch. The headroom is between the 60-7 and the 707, it has great harmonics is the brightest and clearest of the three. This pickup in a Loomis is awesome with a tube amp or a dark amp. The attack can get twangy with the maple fretboard depending on the amp and settings. I have only tried this in the bridge position.
The 707 has the most mids and the most headroom, it works well as a bridge or a neck pup. Harmonics are not as great on this as the others. It is a better neck pickup then a bridge pickup but as a bridge pickup it is my favoutrite for playing Fear Factory songs. It is the tightest of the lot in the bridge.
The 60-7 is my favourite in the bridge position, it doesn't have as much headroom as the others but it still has more gain on tap then any passive I have used. Tonally the 60-7 sounds identical to a Nailbomb bridge in my 2027. If I turned the volume down to about 75% on the 60-7 there was no difference in tone, attack, feel or anything. When I switched between the Nailbomb and 60-7 it was like I was playing the same guitar, but then I can crank the volume and it tightens up and has way more balls. So it is the most passive sounding of all the actives I have tried and if anyone wants to argue that it still doesn't sound passive I'll argue that they don't know how to use their volume and had it in a shit guitar.
The 707TW is better then the 707 in the neck, when use normally it sounds very similar to the 707 but it is not exactly the same, something about it sounds just a little sweeter. As a single coil it is very very nice, not really like any passive single coil I have heard but I like it more. I can't say that I have ever had the chance to play a single coil I enjoyed.
So if I had only one Loomis would I leave 707's in it? No way, they are nice but they are not the best, I still want to try a neck Blackout but based on my current experience I would have the 707TW in the neck and the bridge would be a choice between the bridge blackout and 60-7 depending on the amp but I'd lean toward the 60-7 unless I only played high gain rythm through a darker amp. I currently have 4 guitars with actives so I have a few different combos.