I have never owned either of them, but have looked into them because I am in the market for an ILF riser right now and the Excel is at the top of my list.
The Dorado IS a 19 inch riser. It ISN'T ILF though which means you'll have to buy conversion bushings for any ILF limbs that you want to use on the Dorado. I think they're about $20 or so. When you use these bushings you lose the advantages of ILF limbs. You won't have the adjust-ability that you normally have when using ILF limbs.
I would say the same rules about going to a shorter riser would hold true for the Dorado as well unless the geometry is a lot different than the usual risers. I can't imagine it deviating THAT much from the 2# per inch shorter rule of thumb people often cite.
The draw weight would INCREASE if you use them on SHORTER risers NOT decrease. Your limbs that you have now that are rated for a 25 inch riser would be HEAVIER on the DORADO. Since it is 6 inches shorter, it would probably be around 12 pounds heavier draw weight, give or take, that's not EXACT.
Also it depends on your draw length and whether the length of the limbs is sufficient for your draw. Your limbs on a 6 inch shorter riser might start STACKING on your and if it does you would gain MORE than the 2# per inch. You have to be careful with this stuff as your limbs might not be good to use on a riser that short with your longer than normal draw length.
From my general browsing on ILF limbs, it's not easy nor cheap to get a set of ILF limbs that are 50#. I'm sure they're out there, but they'd be expensive if you get the OLYMPIC STYLE limbs and not the ILF limbs that Lancaster sells that are meant to hunt and are rated at 50, 55, 60 and so pounds.
That's about all I can think to say. I'm sure there will be others that are much more knowledgeable than I am that can give you better and more detailed advice on this situation.
I would say that unless you are just wanting a shorter riser, the 21 inch Excel would probably be your best fit in this situation, definitely safer I would think. Others can shed more light on this than I can.
Good luck and let us know what you decide.
Nalajr