I don't care even if it was totally worthless, to me it's the most beautiful aircraft ever built! A subjective viewpoint, to be sure, but them's my sentiments.Very much in line with the UK's White Paper of April 1957.
But in reality, even in a strategic situation, limiting yourself to only one type of weapon can lead to grave limitations, especially if your intended target happens to move. One of the reason ballistic missiles never completely replaced manned aircraft was for that kind of realization; the need to be more flexible than to simply point-and-shoot. Missiles have their niche, and are indeed needed, but they are not the end-all, be-all answer to every type of warfare, hence the current mixing of manned and unmanned weapons to deal with an array of situations.
That being said, the B-1 definitely has an edge over the B-70. If one removes the benefits of missiles, the B-70 (or at the very least NAA's version of it) still had far too many limitations to really be a game-changer in aerial warfare. Speed was its biggest selling point, not it's weapons load or its versatility to do any other role except recon or high speed research in general. Its one of the most impressive aircraft to be built and flow, that's for sure. But it's scope was too narrowly set, and I think that was realized well before it flew. That, plus the cost of making it ensured it would never see widespread use (a fleet of 15-20 at most could have been justified, at most). The B-1 avoided this curse by being more flexible...It was fast at height (at least for the B-1A), but could also hit the deck and come screaming under the radar, and had a wider speed range in general. The B-70 had just one profile; high and fast. Overall, it wasn't missiles that doomed it, it was that it far too specialized to be of long term use. Maybe it couldn't be shot down because it was so fast and flew so high, but it was still easily detectable, plottable, and predictable, allowing for some countermeasures like moving the target of the area, meaning the bomber will strike an now worthless target.
I like the XB-70, but not enough to think it was more useful than it really was.