[momof4CA]

There are lots of people that train there dogs to do both.

If he is more comfortable going outside and does with out a problem...you might not want to fight 'nature'. It is natural for dog to want to go outside.
What about putting his potty pad outside too.

My dog is about 18 months old. I have a potty pad (in a tray)right inside the back door and one right outside the back door. He uses both. I am hoping to someday only have a pad outside on the porch and not in my family room/kitchen. He will also pee outside...if needed... but not his first choice.

It is very important to teach them to pee on command. I always 'go potty'... for both inside and outside. Then give a 'special treat' (in our house it is cheese) for going!!