Sometimes the originals can be problematic. Several amps require mods to run safely with modern wall voltages. Or, at the least, having a voltage regulator, which is yet another piece of gear to lug around with it. And, you have to worry about taking a value hit if anything original goes ****-up on you. And they're only getting more expensive all the time. Not that that's the most important thing, but life happens and it's good to know you can at least scratch if you need to shuck it in a pinch. The number one benefit, IMO, is they are almost infinitely serviceable if hand-wired.
If I had the choice to get a new, boutique hand-wired version of every vintage amp I wanted, I'd go that route. But no one was making most of the amps I wanted. Marshall plexi clones are plentiful, but no one was making a 50W MV JMP, so I went vintage. Same on the Super Reverb. Allen's Old Flame is real close, but just when I was going to pull the trigger, a vintage one came along at a steal. When I was searching for a Hiwatt, I went with a new Hi-Tone with a repro starfinder cab. Got the whole rig cheaper than I could have gotten just the vintage head. Most recently, I got the bug for a brownface Fender with the 5 triode harmonic tremolo. No current options for exactly that in boutique world. And, I wanted a tube rectifier. So, Vintage Super, it was for the best price to have exactly what I wanted.
I think that honestly, if I could get exact recreations of my vintage amps in the future without compromise, I would probably do that just to get that worry about losing original transformers off my back. It's nice to have the real thing and feel the nostalgia, but for me, the sound of the unique circuits trumps all.