Size is an important factor when considering your paving and 250mm x 150mm is a large sized Block Paver. Giving enough strength for a driveway paver considering the depth.
If you use smaller slabs they may be easier to handle than the larger sizes, which may be an important consideration if you want to complete the job without help.
Conversley, the larger sized paving slabs will need less grouting because there won't be as many gaps
