If you can only afford one or the other, hmmm. IMHO I would go with springs, you already have a decent bar. The springs help in handling and makes it look better . I just installed a Alta 22m rear sway bar, not to expensive.

 

Lets try to stay on topic.

Springs are for general handling and can affect ride height (appearance and function) and come in a variety of ratings from comfortable for street use to very stiff for track use. Labor for installation is a bit more than for a rear swaybar.

Swaybar is usually adjustable and for the rear. Comes in different thickness which affects stiffness but you cannot see the difference and it hardly affects ride quality for daily street use. It does help to reduce understeer when set to the correct level of added stiffness when doing high speed cornering.

If you are happy with your ride height and quality and you do corner fast then adding an adjustable rear swaybar makes more sense.

If you want to adjust ride height (a little or a lot) and improve handling overall then springs make more sense.

If you change springs and your MINI is older with at least 50-60K miles then changing shocks at the same time makes sense.

 

what, if any, are the major differences between h-sport, M7, H&R springs and, TSW?

 

I would start here: Sticky: Wanted: Aftermarket Spring info ( 1 2

 

This is pretty much the reason we stuck with a conservative drop and a linear rate spring - mild lowering, good ride, and stellar performance for AX and track work. Another TSW-spring equipped MCS won their autocross class at today's LSC BMWCCA event - par for the course!