You can play freeciv in civ1 mode - i.e. with civ1 techs, units, etc. When I do play freeciv, I ONLY play it civ1 mode of course. They got it pretty close. One difference that comes to mind though is that there's no diplomacy at all. (You're always at war with all other civs, and the AI is cold and ruthless!)
On the plus side you have more choice of number of civs and size of map. I once played 30 civs on a huge map, and the game went on and on and on and on. I was losing, 5th out the dozen or so remaining civs. The gameplay was weird at that point, a combination of hitting coastal cities with battleships and trying to colonize the still-vast unclaimed lands of the world...
IMHO civ1 is much better because of:
* nostalgia (probably the prime reason I like civ1 anyway
)
* the graphics (probably related to nostalgia)
* the AI - this is really important - freeciv plays VERY differently than civ1. If you like to play the game like chess, where the rules and setting of the game merely provide a structure in which you can test your wit, then YOU might like FreeCiv better (both because of the AI and because you can play against human opponents). But if you like to imagine that you are playing out world history through the ages, perhaps playing a more civilized game, etc. then the civ1 AI is much more amicable.
* little niceties - civ1 has all the finishing touches of a commercial game. freeciv doesn't have as many little graphical and animation touches.
