depending on climate, and ride frequency, it boils down to how much you want to spend, and if you believe in the manufacturers...
a lot of the 14AH batteries, that are noted as such, like the YTX14-BS, which is really the BS thing, as it's a 12AH unit, are in fact 12 AH, but that is only a factore of how it "stores" power, and the real point is "cold cranking AMPS", or, in reality... how much capacity does it have to "deliver" the stored amps. Plate designs and configurations, along with the chemical composition of modern batteries, vary greatly, some break down internally, some chemically, and most with a combo of both... charge/discharge cycles, and the use of battery "tenders", make it even more difficult to predict the true failure point, between "worked fine" to "dead as a door nail.."
I try to use good viable manufacturers, Exide has been pretty much a standard for "ok" and priced as such, but higher end AGM's, with Higher prices, may work better, or not, sometimes.
The cheapest 12AH, with 200CCA, seems the most realistic, it's all the bike "needs", but I always prefer a larger CCA rating (220, or above), when durability is the main key.
the more I look at the 14AH batts, the more I'm realizing the manufacturers have done a "sidestep", and are using this XXXX-14BS rating, more often as a specific "format SIZE" (physical dimensions), in lieu of actual capacity today... and really chincing out on the customers... giving a 12AH unit, packaged in what was always a 14AH package size... pretty cheesy in my opinion...
I've sent numerous e-mails to Odyssey, asking them to make a "package size" suited to be as we need, but have never had any luck with them accomodating it, with the size of the C14's "package", the Ody batt would be capable of over 240CCA/14AH easily.. they get that out of smaller batts currently, but the terminals are backwards... unfortunatly.
these cost, but seem fine....
I do caution about the first one,a 16-BS, as the height excedes the "package" height
the rest are the correct size...
Xtreme AGM Battery for Kawasaki FTZ14BS Replacement
16-BS
Lead Acid Type: Starting
Cold Cranking Amps: 230
Warranty: 12 Month Free Replacement
Weight: 12.05 lbs
Length: 5.938 in
Width: 3.438 in
Height: 6.375 in
Item Number: CYL10012
Brand: Duracell Ultra
Voltage: 12
Format: 14-BS
Lead Acid Type: Starting
Cold Cranking Amps: 220
Warranty: 24 Month Free Replacement
Weight: 11.5 lbs
Length: 5.87 in
Width: 3.38 in
Height: 5.75 in
Item Number: CYL10001
Brand: Duracell Ultra
Voltage: 12
Format: 14-BS
Lead Acid Type: Starting
Cold Cranking Amps: 220
Warranty: 24 Month Free Replacement
Weight: 11.5 lbs
Length: 5.87 in
Width: 3.38 in
Height: 5.75 in
Item Number: CYLA14BSXTA
Brand: Xtreme
Voltage: 12
Format: 14-BS
Lead Acid Type: Starting
Cold Cranking Amps: 200
Warranty: 12 Month Free Replacement
Weight: 10.25 lbs
Length: 5.94 in
Width: 3.43 in
Height: 5.79 in