Rail networks take decades, centuries even, to achieve their full potential as development goes up around it, usage patterns adjust and networks are added. Best to get rail in as soon as possible, but make sure it's the right system, and future proofed.
Good on Ottawa for grade separating it's system. I believe Calgary made a big mistake on not grade separating the LRT, especially across some major roads and especially especially downtown, which is painful to ride across.
I think there have been fairly some nonsensical arguments between 'LRT' and 'subway', mainly due to the fact that there is no single definition of either. LRT can mean pretty much anything, but generally just means lighter vehicles. The
Docklands Light Railway is classed as light rail, but has no at grade crossings, has deep level underground stations, long vehicles and carries 300,000 people a day. It was built partly on old heavy rail infrastructure but has the advantage of being able to make much tighter curves and handle steeper gradients. Vancouver's Skytrain, too, is light rail.