Finishing Liberalism later (but still being first) works out better (at least, looking at the results). Base culture is probably more important than early Liberalism.
This weekend I have come to a very similar conclusion: the date of Liberalism is not as important as the number of temples/cathedrals you have built at 1AD.
When I wrote the first post of the sub-1000AD thread, I thought that the special thing about that game was Liberalism in the BC (and high number of GP). I worked hard on improving that, bulbing lots of GS, for example. I don't have problems getting Liberalism in the BC with a single GS, now. But I didn't improve my date. Why? Because the importatn point about that game wasn't the Liberalism date.
It was the early settlers and the high amount of food in every city, which allowed me to whip lots of missionaries and temples in all the cities at the same time.
Slavery is a civic, and as such it affects all your cities. When your GPFarm is ready for artists, soon before 1AD, your other cities must have finished whipping. Other cities that are behind in developement must do without slavery or your GP generation will suffer. So you want all of your cities setted at more or less the same time, so they can all be aligned with your Slavery-then-Castes timetable.
An example of the wrongness of prioritizing research over hammers is this:
Eli, BTS, inland sea. Corn+2gold+5FP start not on a PH. I research Wheel-Pott-Myst-Medi-PH-Wri-CoL. Since I haven't researched agriculture not Alpha, I ignore the corn. Quickly build a bunch of cottages and grow, then work the golds too. Build Worker-Warrior-Settler-Oracle.
CS slingshot done in turn 62. The same turn, they trade me Alphabet. Settler has travelled far, towards a religion founder AI, so it gets the second spreaded religion. It has a lot of FPs and Marble, will be GPFarm. I have founded confu. I am in the best of positions, aren't I?
No, I am not. Without marble, my worker has had to stay in the capital to chop 4 forest pre-Maths on Oracle. So my GPFarm has to build a Worker at pop1, puaj. My next settler is a bit late, so it can't get the bananas and settles without food resource, with 4FP, copper and a lot of grass. 4th city in a disgusting place, nothing best left; very late too, turn 84.
I run Bu+CS for a short time to get my Academy without a Library. Then revolt to Slavery+OR. But here comes the problem. My 3rd and 4th cities have just been settled and have not pop enough to whip their granaries. My 2nd and 3rd cities have not a food resource, so whipping is not very interesting. My capital has to feed 2 goldminers with a single corn, so bad excess food and bad whipping.
Used a GPro on a GAge to reach Liberalism in the BC and save 2 revolution turns. But nobody would trade for Music yet. So I went into 100% culture without a single cathedral built. NE built as late as turn 118. I finished Hermitage in turn 133, without Music yet (I had not the temples built anyway). Taj Mahal and revolution to Merc. Victory in the late 16th century.
So the CS sling was bright researchwise, but delayed my expansion and didn't result in a good finish date. I will be playing without early wonders from now on.