I am rebuilding my bike fitness and was wondering the effects of slow long distance training vs maintaining a decent average speed.
What difference it makes if i choose one of the above?
It depends what sort of bike fitness you are trying to build, your current level, and your riding history.
I'd start by saying that simply trying to maintain a high average speed is a poor training method for anything, and I think you'd struggle to find a coach that advocated such training. It simply produces fatigue without actually going hard enough to produce significant training stimulus.
Long slow distance (LSD) will predominantly build your endurance and your ability to burn fat as fuel rather than carbohydrate. If you are targeting long distance rides then these are an ideal starting point.
If you are more interested in shorter events like 90 minute criteriums/XC mtb then building a large endurance engine is not so valuable, and you are better off targeting short hard efforts (2x20's, 5x5's, 30/30s etc) to build your speed.
For most people, a combination of both is going to be best to become a strong all round cyclist. There are any number of 'sportive' training plans on the web that will help with this. British cycling have a range of Training Plans for beginner to advanced that are free to download.
I think that depends on what you want to achieve.
If you want to be able to ride 100 miles then go for distance, if you want to be competitive on your local 10 mile TT then train for speed, if you want to be a fast hillclimber then go ride some hills etc...
Outline your targets first, then find out how best to train in order to meet them. They can be very simple, like 'keep up with the base group in my local club', or 'ride to work 5 days in a row', and build up from there.
The answer is neither really...
Not the answer you really want to hear, but it all boils down to:
What do you want to achieve?
The core answer is Intervals, Intervals and more Intervals.....
I repeat they HURT!
But you will improve in leaps and bounds by doing them.
To get a more rounded type of fitness, distance is your only man.
Distance cycling at a certain threshold will help improve your endurance, as Interval training improves your fitness and cycling strength.
Please note: I do not work for Bicycling.com, but it is a good reference site for those starting off.
Please note this note: If you want to really work it, get yourself a training plan from a Coach and you'll be flying in no time.