When you upgrade your vintage bike do you like to upgrade to more modern components
or do you like to keep it original? I myself like to keep the bike as close to original as I can.

I do both. Just need to make sure you have enough bikes.

I try to keep it as original as possible while allowing sufficient modifications (primarily gearing choices) to allow me to ride it in the places I like to ride. If I kept all my bikes totally original (i.e. with '60s criterium gearing for example) I wouldn't ride them. This is why I have added an additional small chainring and longer RD cages to several of my bikes.

Depends on whether you want to ride them or hang them on the wall.

I never try to keep a bike original, unless of course the original represents the best in the components I want. For me it is all about improving the bike, enjoying the ride more for how I want to ride.

For example, to help my wife with trigger shifters and brifters, I installed rapid rise/low normal rear derailleurs. Everyone hates them. I started running them on my mountain bikes. They are great. Things change suddenly and I can dump a cassette faster than anything else. I’ve got them on all my trigger bikes.

John

I don't try too hard to keep things all original, as I see that as impractical, and my bikes aren't super-special grail bikes.

[edit]
It depends a lot on the bike.

With my Bianchi Megatube, I would always keep that period-correct: e.g., I wouldn't stick a more modern (outboard cups) BB on it. 8-speed Campy Record and a square taper BB is what it should have, and that's just fine.

But the entry-level aluminium M Alloy Pro, or the steel Colnago, sure why not put whatever on it?

I go for original or with period and make correct components. I purchased my Legnano Grand Premio as a frame/fork set. I built it up with what I had that, at least, looked the part. But as time went on(several year now), I added NOS Legnano cottered cranks and bottom bracket, Legnano embossed head set(still to be installed), Legnano Pantographed Campy High Flange Record hubs laced to 700c clincher rims, and a Campy Record transmission.

All of the above elevates my GP beyond the components offered at the time. But all of the components are pretty darn close in vintage and obviously Legnano, so it works for me. The clincher rims, incidentally, were swapped for the tubulars that I tried for a while. The bike still sports its patina and I still resist the urge to paint. Anyway, getting closer with my hut for this and that. I really enjoy the hunt for the next needed piece...