Your choice of lawn bowls will depend on many unique factors, and at the end of the day will boil down to personal preference and the requirements you have for how you play. These will include what position you play, where you play and how you play! There are a number of options available to you whether you play indoor or outdoor bowls. Variations in bias and size and weight of the bowl will be the main options you'll need to decide on when choosing your bowl.
It can be quite a tricky task, especially if you do play a mixture of indoor and outdoor bowls and only wish to purchase one set of bowls. You may have to compromise somewhat and choose a bowl that suits the indoor surface predominantly and use them to the best of your ability for the outdoor games. The variation between a slower often wet and heavy outdoor lawn is just too great compared with a faster indoor green. You won't find any one set of bowls that is suited to both conditions and unless you choose to buy two differing sets of bowls a compromise will need to be made.