Cheers...

Best doing some of both.

Both will help you lose weight in different ways. If you keep the intensity on the weights workouts you will still feel your heart beating faster. Depending on what type of gym your at you may be able to set some intense circuits up. (Depending on current fitness levels)

Make sure you change your workouts every 4-6 weeks so your body doesn't get used to it.

Ultimately, your diet will have the biggest effect on fat, muscle and weight loss.

I shifted a stone at the start of the year by eating more healthy and doin about 3 hours a week at the gym on the bike, cross trainer, rower and some small weights.

What I learned though is that your body stores fat in key areas and no matter how much you exercise that particular area you won't lose the fat from there first. In a male body for example the main storage area is the stomach and so no matter how many sit ups you do you will still lose fat from your legs and a$$ first.

If it's just weight loss you're after rather than fitness simply cut 3 things from your diet

Sugar, your body doesn't actually need sugar.
Wheat
Dairy (milk)

Remember Sugar in foods is sometimes called something else to try to fool you
Dextrose, Fructose, sucrose etc etc

Simply cut those 3 things out and you'll literally see the pounds drop off you.

Oh i say simply, it's very very hard.

Cut out fruit except avocados and on the veg side no Tomatoes or Carrots too.

It also means alcohol is out of the question (wheat) and no white rice (sugar).

I went from 16st to 12st 8lb in 6 months without a shred of exercise and felt good after the initial sugar shakes (sugar is apparently more addictive than heroin)

That's some willpower. As I don't have that, I need the exercise. Not been the gym for a while now as I don't have that same drive that I had at the start of the year but I'm trying to set myself a new goal to push myself into going back.

once you get a bit of fitness try some cardio stuff outside of the gym. cycling or running both great forms of exercise and getting outside takes away some of the monotomy of the fixed bike/treadmill. also try to have several smaller sessions a week rather than just 1 or 2 long ones.

initially after a good gym session you will get stiffness and some muscle pain. this is normal as the body is toughening itself up for the next expected onslaught. after a few sessions you will get stronger and the pains will vanish

one final tip i would give is never to reward yourself with treats for completeing some exercise if you are aiming for weight loss. you can end up taking more in than you are losing. its frightening how little of the wrong foods can spoil an hours work in the gym