Realistically whichever is in the best condition will be the preferred choice.
Generally the smaller Startrite drills were a little more woodworking orientated and tended to have rather higher speeds than desirable for metalworking. Even the ones with the reduction gearbox might be considered a bit on the fast side.
If you see yourself drilling lots of 1/2" holes in metal I'd be looking at the Elliott first.
But speed range is generally not a deal-breaker providing you have 100 rpm or thereabouts for the bigger drills. The ordinary belt drive Mercury is too fast for general purpose metal work tho' and can burn up drills.
Clive