Further or faster????

A bit of a newbie to running, i've always been into weights.  i'm 18st now and want to cut down to 16.5/17st, mainly to do with my golf swing lol. But also cos i'm getting old now and want to live forever!!! (30 years old)
 
i've started running and really enjoy it.  the missus will drop me off somewhere and i have to run home, (my motivation to not quit half way through).
 
Basically my question is, should i be making my runs longer or make my times quicker on the same route.  i'm only doing 2 miles.
 
i know its gonna boil down to calorie intake and calories burnt, solid diet etc.  But would the above question have any difference in results?

Four options for you to think over:

1) Mix longer runs and shorter runs in different sessions varying the intensity accordingly. Say one long slow run per week and a session of 3-6 400m runs

2) Do some form of interval training which includes fast and slow intervals and/or fartlek type runs.

3) 1+2

4) periods focusing on distance mixed with periods of time spent focusing on speed

It's up to you mate, how you;re enjoying it and how you body is coping with the runs (especially the knees) as no matter you build 18st is a lot of weight to shift around and the legs will be taking a pounding.

yeah the joints are ok so far, but i've only been out 4 times.  i find myself making shorter, lower steps to limit the force of my weight going through me.
my calf went last week, so i find myself  running more on my heels to take weight off my calfs, but now my shins get a huge pump because of this. 
Just gonna take time to build up the running strength in my lower legs.