BTB advantages:
Trim line always in reach.
Longest amount of theoretical bar throw available
Naish specific: suicide mode depowers the kite in event of a release (this is really good for freestyle)
Less bits to get caught up whilst wrapping the lines (Naish T adjusters on their older bar tangle easily)
Potentially lighter system
BTB disadvantages:
Trim is difficult to adjust whilst riding
Many systems slip and are difficult to adjust by small amounts
Swivel is high on the lines and is difficult/impossible to get it to work if it isn't
ATB Advantages:
Trim is easy to do on the water on the go
Higher level of trim potentially available (assuming adjustable cleat e.g. Best/North/Switch) which can help stance
Swivel tends to be at the QR which is gives a more reliable untwist.
Easy to make micro adjustments to the trim
Probably more points but these are the usual ones. I prefer ATB. Except for the old Naish one (webbing strap version). That was rubbish. All the worst of both systems in one. Yuck. The new ones look alright.
Or....... get click bar?
