Which is better for a torch lighter?

Both work in butane torch lighters. The Xikar's low-impurity spec and high-altitude formula suit precise torches and mountain use; the Zippo's large can is fine for routine refills at low altitude.

Which lasts longer between refills?

The Zippo can holds about three times the fuel of one Xikar can, so it covers more refills before you need a new can.

Is the Xikar worth stepping up to?

If you light at altitude or want a documented low impurity level, yes. Otherwise the Zippo does the same job with a bigger can and a solid owner rating.

Does either one clog lighters?

Both claim the opposite: Xikar says its formula clears built-up impurities, and Zippo says it will not clog burner valves. Impurities in any butane are the usual cause of weak flames.

Can I fly with these?

No. Butane fuel is a hazardous material and is not allowed in carry-on or checked baggage. Xikar also ships ground only.

Which is better for a travel kit?

The Xikar's 1.9 oz can packs smaller. The Zippo can is bulky but needs refilling less often at home.

Xikar Purofine Premium Butane vs Zippo Butane Fuel

Both are refined butane for lighters; the real split is can size and formulation. The Xikar Purofine is a small 1.9 oz can with a high-altitude formula and under 15 ppm impurity spec, aimed at torch lighters and travel. The Zippo is a single large 5.82 oz can rated 4.7 from 92 ratings and marketed on not clogging burner valves. For most shoppers the Zippo is the simpler, longer-lasting pick; the Xikar suits high-altitude use or a compact can.

Choose the Xikar Purofine if you light torches at altitude or want a small can that fits a travel kit.
Choose the Zippo if you want one large can that lasts through many refills and a strong owner rating.

Prices

Xikar Purofine Premium Butane: $9.99 at Xikar (checked today)
Zippo Butane Fuel: $8.49 at Walmart (checked today)
Difference: the Zippo Butane Fuel is $1.50 cheaper than the Xikar Purofine Premium Butane today