I have come full-circle on this one today;
On first playing the Nailbombs I thought "Yeah, that sounds really good. Just what I wanted!", then playing with them a bit more I began to question whether they really were "Just what I wanted" (hence the doubtful tone of my previous post) then I moved the bridge pickup one turn closer to the strings and it all suddenly filled out. Next, to be really sure, I even did some side-by-side recording with the Rebel Yells in my other Eclipse so that I could do a proper comparison. OK, so what's the verdict? Output wise (in terms of peak volume) there's nothing in it but the NB bridge sounds fuller in the bottom end and has that trademark raspy attack where as the RY is busier in the upper mids. Which do I prefer? For 90% of the stuff I play, the Nailbomb will be the better choice. Now, as for the neck - this is a bit trickier. I remember reading that the RY neck was designed to be something of a compromise between a VHii neck and Cold Sweat neck, possessing the best bits of both - which it pretty much does, making it a great pickup for cleans and strat-like leads. The NB neck on the other hand, is harsh, aggressive and better suited for crunching rhythm than leads, however it does also clean up quite nicely (especially when coil split) for something a bit more funky.
So, in last 24 hours I started off loving the Nailbombs, then had doubts about them and then went back to loving them again (especially the bridge) - the turning point came with that one extra turn of the screw. The question now is that since I have the Nailbombs will I still use the Rebel Yells? Only time will tell.