Battery for gliders

I bought two Panasonic 7,2a/h batteries and I am very disappointed.
Lucky for me I had two Yuasa 7.0 a/h units, one of which was still in good
working order. I was able to get a direct comparison between the two.
Both Panasonic batteries show at least a 25% less performance compared to
Yuasa. This is the usable time everything being equal.

Also after "identical charge" of all three batteries the two Panasonic's
always
show the same 12.52 volt with the surface charge removed.
While the Yuasa always shows 12.76 volts.

Was I mislead by the Panasonic spec sheet?
How come the old Yuasa outperforms the two new Panasonic,
despite the fact the Panasonic is rated higher by .2 a/h ?
How am I to select the battery if I can not trust the spec sheet?
Is it all reputation. Please advise

Regards
Udo