As far as I can tell it's just a Japanese [square] Vs. European thing [straight].
I don't think you'll notice a performance difference on this alone. The phosphor combination used in various bulbs would make one bulb better than the next.
Performance is the same, granted same phosphors used. It's nothing more then a difference in electrode alignment. Differences in price would reflect differences in currency exchange, import tariffs, etc. Both types of bulbs are readily available nowadays.
Leonard made a good point here about the phosphors. IMO different companies are using different phosphors and getting different color temperatures. Custom Sealife seems to favor the Japanese square pin, while Jalli, JBJ, All Glass, TAAM seem to go with the straight pin. Energy Savers has some of both and some of the others do too. I don't know if one is superior over the others or not, but I do think that certain bulb lengths by certain manufactures are only available in certain pins styles. To add to the confusion some of the above are different companies that are probably buying from the same OEM.
I would suggest finding the bulb brand you want first and then making sure they offer the pin config of the fixture you are buying. Most of these companies advertise in fish mags and have web sites so good luck.