Are more expensive brakes noticeably better?

The brakes are cannondale delta. Does anyone have an idea what these are
comparable to in the shimano range? Will I notice an improvement with a
more expensive set of calipers or would I be able to make up most of the
difference with a better set of brake blocks?

Two things have a huge difference: brake blocks and set up. Kool Stop
Salmon brake pads are recommended here (they're designed for braking in the
wet), and getting the brakes set up with minimal clearance (a couple of
millimetres?) has a h-u-g-e effect. Brakes on my hack are rubbish most of
the time, except when I've just adjusted them - can do stoppies with ease
[1]. Wheels do need to be true to get the brakes adjusted properly tho.

Having said that, it's definately worth having decent brakes. The cheapo
ones on the hack are a little stiff and not really working as well as they
should be. In contrast some Shimano 105's taken off a wreck dumped in
someone's front garden for over a year are still as smooth as they day they
left the shop. Don't know what your current ones are like tho. Definately
worth setting them up properly with the Salmons and seeing if that works
first - even if you decide to buy new brakes you'll be wanting the blocks
anyway.

The back brake doesn't do anything when braking hard so consider spending
double the amount on the front brake and keeping the old rear.

Would changing the brake cabling do anything (assuming it's had a few years
of use)?

[1] Like a reverse wheelie.

Mark Thompson wrote:
Two things have a huge difference: brake blocks and set up. Kool Stop
snip

Wot 'e said matches my experience of Kool Stop pads since 1987 (and
those were just the gray ones). I still have some 1980's vintage
callipers which provide excellent braking with the Kool Stops in them.

--
JimP
--
"We don't have a plan, so nothing can go wrong" - Spike Milligan