I have camped at both Sprague Creek and Avalanche numerous times.
I prefer Sprague Creek for the reason listed above and its right on the Lake.
I prefer Avalanche for hiking up to Avalanche Lake and for an early state Eastbound.

Note -
The new road closure is from Apgar to Logan Pass in BOTH directions from 3p to 6p.
That makes it tricky for westbound cyclists - and even biking back and forth to the Lake McDonald Hotel and camp store.