Replacing a cam isn't a trivial task, and I would only bother replacing one when either the cam is bad (flat lobe) or the engine is apart for some other reason.

When replacing a cam you should always replace the lifters as well. This involves pulling the head off the block. The cam gears are a notorious weak spot, so if you have a fiber gear replace it (you rarely if ever have to replace the steel crank gear - it just doesn't wear out against a fiber gear). Replace the brass thrust washer behind the cam - when it gets worn the cam can slop back and forth at idle and make a fairly benign but irritating clatter.

There is no magical cam that makes everything all better. They all just optimize the breathing at various rpms points. Some 'racier' cams probably would end up making less power in an otherwise stock engine, as the breathing upstream and downstream can't sustain the proper flow at the cam's tuned rpm.

The only cams I have personal experience with:

'C' grind cam - standard in most non-FI two carb Volvo engines in NA. Power peak is relatively low, torque falls off before redline so you are rarely tempted to zing the engine.

'D' grind cam - standard in about 1/2 of the FI B20 engines, exceedingly similar to the 'K' cam used in the other half. Probably the reason behind much of the HP increase in the B20E engine, with those unobstructed FI intake runners being the rest of it. Has a more pronounced 'on cam' sensation at around 2500 - 3000 rpm. Definately revs higher, pulls nicely up to the redline but not past it. A very nice improvement for any 'C' cam engine

IPD Street Performance cam - a modest improvement to the D cam. My butt dynamometer indicates that it has a slightly higher power peak, but that the torque below that peak is a little less.

I have an 'R' cam that I'll be putting in my PV's engine over the winter. Possibly I'll hate it - I'm certainly not getting rid of the 'D' cam in there now.