on axis or off axis? well ur answer is not goin to come as easy as just saying it or by following peoples experiences, cause u got to take into account regarding your own car "environment" or acoustic of ur own car ..eg waja car on axis 30deg on da a-pillar is not goin to sound the same as in a camry or honda etc..
not to mention what sort of equiptments u r using to drive ur units, tuning and da list goes on and on..
it all comes down to u placing it in ur car (a-pillars, sail panels or kicks) and at diff deg on/off axis then start listening to it start appreciating to every single changes u hear, tune until it sounds gud for u den u can say it sounds better on or off axis..damm im still doin dat

BUT of course there r general things dat u'll hear people say ring radiator is more directional compared to domes blah blah blah not to say its wrong and all ::)
what counts is at the end of da day u got to DIY and njoi da experience of it..im njoing it but sometimes it gets so damm f#@$%5 frustating just bcause u cant get certain freqs to sound good