Night and day! Not to be an SA , but their is no comparison. The RO/DI has gone through several to may steps of processing (depending on the stages and size of the RO unit)to remove contaminants, heavy metals, unwanted minerals, all kinds of nasty things. The "water conditioner" in a bottle usually is only good for removal of chlorine and a few other items. For my $, ro/di is the only way to go.
In this hobby, quality water - quality lighting -
keith