That’s an amusing brain teaser but I have an opinion.
The Brewers magic number to ensure finishing ahead of each of the teams is 17 so, from that standpoint, the leads are equal. But, because the Phillies have one more game left to play, than the Cubs, there is one more game in which the Brewers can pick up one of those 17, so the lead over the Phillies is very slightly more comfortable.
As a rule of thumb, now that the Brewers have clinched the tiebreaker over the Phillies, a lead of X games over the Phillies is equivalent to a lead of X+1 games over the Cubs
I know there is some sentiment that strength of schedule is largely irrelevant, but the Phillies have a tougher remaining schedule with upcoming series against the Mets, Royals, and Dodgers, all teams fighting for playoff positions.