Interesting question actually. Dion is known for blending cigars to age well, and some of my aged Singulares have been among the finest cigars I have ever smoked, but even the original Phantom isn't really that old in the cigar world. Hell, the company has only been around since 2005, so no one knows what an 18 year old illusione tastes like and it will be a while till we do.
Cuban LEs have started to get the opposite reputation, with many people now saying that unlike many regular production Cubans, LEs are best within 5 years. Tobacco strains have changed so much in Cuba that most people are saying today's cigars are way different than pre-2000s blends. No one knows if they will age for decades like they used to.
18 years is a long time, so I dunno. I would bet on both being past their peak at that point. Id put that same bet on any modern cigar right now, so if I was serious about putting something down that long and not touching it at all, I would vacuum seal it to slow down the aging process.