I have done both of these in a progressive kind of way..!
My engine was originally an SPi that was pulled from a wrecked 95 cooper, and then ran on twin SU's when I bought it. I had the engine re-built after a gearbox failure and re-bored to 1293cc, correct pistons to provide lower compression and re-built cylinder head with larger valves. My plan was always to install a supercharger even before gearbox failure.
My first setup was HIF44 carb and dizzy (simon bbc), then went to mega jolt which made the engine run so much smoother, and make the most of things. This setup alone was great, and had it not been for carb icing i would have stuck with it. By the way mine is not a daily driver.
I installed a carb heater from SU, yes its actually a part and is a +12v collar that goes round the dashpot. I also put a heated element in the air filter. I would like to believe these helped but I dont think they done much expect thinned out the dash pot oil. I have seen some people on here use copper pipe connected to the engine cooling system wrapped around the inlet to help cure this. One guy on here has actually fabricated an alloy tank around the inlet thats plumbed into the engine cooling system - quite an impressive piece of work..!
My inlet snorkle did ice up summer or winter, due to the fuel evaporation it causes ice to form on the pipe from carb to supercharger. This is not carb icing... which I believe is due to moisture building up within the carb and the constant flow of cold air (summer or winter) makes the moisture freeze. Have a google on it.
So, next thing I looked at, to cure this and also add further tuning capability and smoother running and also fuel economy as a by-product (but its made a huge difference!) was fuel injection using Emerald ECU. Another inlet to take injectors was made up, I used two injectors, and also to accept the throttle body. It was a lot of effort, and needed a few more parts such as MPI fuel tank, adjustable fuel pressure regulator, few lengths of fuel pipe, and of course ECU kit with all the sensors, but can say its worth it. I know power figures are rolling road specific, mine was mapped last week at 149 at flywheel. Engine has done about 900 miles since re-build so still being run in etc, tuner has mapped to 6000 rpm and reckons a few more hundred miles and oil change to 10w/60 can map to about 7000 rpm not that I will be using that...!
Main reason for getting the car more up to date with fuel injection was the potential carb icing thing leaving me with no power, which happened on busy A road with little run off with my two sons in the back. I can say that barring any other mechanical failure I have every confidence in the setup now, and could easily use the car as a daily driver.
Driving wise, its a bit of an animal. I run 10" wheels, 7.5 s discs, hi lows with standard but new rubber suspension units all round, solid subframe mounts, neg camber front and rear, this all needs to be set up correctly, but as its all new am waiting for things to settle in..! Had a few teething issues with ECU over fuelling but with time, more miles and re-mapping this has now been resolved. With further re-mapping after engine has had a few more hundred miles on it I am hoping it will have smoothed out the power curve somewhat.
Engine build and tuning all done at VMAX in Surrey.
PM me if you want some more info, costs etc although as a rough guide £1200 to £1500 for the charger and ECU etc would get you started.