Ive owner them both at one time or another -Both great saws.
The excalibur is more agressive and a bit smoother running - but it costed more.
Not sure if the newer models are- but they were back then .
The Rbi is your standard parallel arm saw - very durable -high quality .
You could run that night and day and its a work horse .
But ive read the older models can be a pain to get parts for -but even when i had the one I had
I felt you could repair or make a few of the parts yourself .
The Excalibur is as well a work horse -but a bit touchier -
I liked it as well -When i bought my Eclipse neither saw , saw too mauch action so i
sold both to friends ( both of those saws are still running -wish i kept both of them )
But i own so many saws ( including many treadle models and toy models -its insane -last count around 50 )