Brakes - cable vs hydraulic

currently have cable disc brakes and am having to adjust them after nearly every ride, which is getting very annoying.
almost like having nearly no brakes by the end of the day - either cable stretch or wear on the pads.
front one is now vibrating the front wheel after last nights dirt crits, but was fine prior to the crits.

the cost to upgrade to hydraulic (where this constant adjusting isn't an issue) seems rather steep.

what are peoples thoughts, and which hydraulics are preferrable - avid juicy's or shimanos??

I use hope hydraulic disks and am very happy with them. A bugger to set up and a bugger to break in, but awesome when set up correctly and stay setup correctly. The modulation is the best that I have come accross, but they are among the more expensive disk options.

I've got Shimano disc's on my Trek and am getting pretty P'd off with them. I have a pretty big descent to do on one of my training routes and they fade out really badly about half way down, so much so that by the bottom I almost have no stopping power at all. The disks then expand in the heat and end up rubbing on the pads for the rest of the ride.I find the pad wear excessive they only seem to last less than 100 miles.

Adjusting is a pain, and the bike is going back to the shop again this weekend to have the rear wheel adjusted yet again so that the disc doesn't rub on the caliper. I'm considering junking the read discs altogether and getting a V brake set up for the back and only having the disk on the front.

Or perhaps I'm doing something wrong, any tips from anybody?

Just my opinion; hydraulic's are well worth the upgrade money (certainly in UK conditions) - I have hope mini mono's on my mtb, and shimano deore disc's on my cyclo-cross (which I also use as a commuting bike to get to work) - I fitted both sets myself, and both have been fit and forget!! changing pad's is simple (a spot of copper slip on the back of the pads when fitting stops any squeal), half hour peddaling up and down the hill I live on to break them in and leave until worn out! better all-conditions breaking, no rim wear - no messing about with them. (i bleed my hope's last year as I changed to goodridge cables, even that was fool proof) - the shimano pads are cheap, but the brakes don't feel quite as nice as the hopes (i've had less pad life out of the hopes), but for the price it has been hard to fault them! If i were buying now, I go with the avid's - because they look sexier, price is good and no-one speaks badly of them

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---------------------------------------------------riding is a privilege - don't be a ****

Yeah, cable brakes can be like that! I would go for Hydros if you have the money but if not, look into Avid BB7 cable brakes. My mate uses these and i reckon these are better then many lower-end hydro brakes in terms of reliability and braking power. They have knobs on both sides of the caliper which offer easy adjusting...no tools required.
With lower models of Hydro brakes (such as Hayes Sole etc), they only have the one piston and are prone to fading, blown hoses and heat problems. So as a base, look at the HFX-9s as they are a proven model and are a good brake. Judging by your post however, you havent included Hayes as a possibility...it really depends on what model of shimano hydros your considering. My friend used to run XT's on his DJ bike and they were awsome...so responsive and they dont lock up at the slightest touch like Hayes HFX-9s. But the down side is they are expensive. He is now getting Deore hydros which are a lower model and i reckon you should check them out. I cant really comment on Avid hydros as i have never used them but i hear all good things about them.

my lbs doesn't sell Hayes. only shimano, avids and hole, hence the options.
will be going with the XT's.

Nice choice man!
A mate and I once went riding to some secret jumps and to get there, we had to go down a tricky decent. He was only running a rear brake at the time on his dirt jumper and it held him pretty good without locking up or skiiding so it gets my vote.
Good luck.