Early New Republic VS late clone wars old republic.

the new republic after endor VS 19 BBY republic. I think the old republic would win because they have battle hardened clones, and powerful jedi because the CW weeded out the weak jedi and the weak clones. And many more resources, but I think the NR had a small technology advantage and also had battlehardened rebels.

After Endor the New Republic barely exists, with a handful of worlds, so yea, Old Republic definitely wins.

Tech improves, ships tend to be bigger in the NR time, but it's not too drastic unless you go for distances much further apart. Basically they'll want 2-3 Venators for every Mon Cal, which is no problem when they have 20-30 Venators for every Mon Cal.

I don't think the NR could win until.... hm, not Thrawn or Dark Empire era, plus rebuilding time... maybe 18-19 ABY? And the OR still has more Jedi even then.