I think a cross bike is head and shoulders above a "road" (modern racer) bike for long rides/tours... The reason is a lot of cross bikes are designed a bit more relaxed with a little longer head tube... The only downside would be if the cross bike had a higher bb which is becoming less common (higher bb= a little less stable in a straight line)...
The other major benefit is you can run much larger tires for added comfort with VERY little performance trade-off and fenders if needed....
so, no I don't believe a true road bike has any advantage over a cross bike in this intended application other than maybe one pound of weight which is nothing over a century or brevet....
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