I'm planning on buying my first AR-15 and would like your opinion.
Is it better to buy a complete AR from factory or to pick and choose your preferred upper and lower?
It all depends on your anticipated use for the rifle. If you are planning on competition or your looking for great accuracy, the better known smiths will give you a superior product for about the same cost as their factory brethern. If you are planning on a fun gun, you might want to consider one of the discount parts houses for an upper. However, the lower cost may or may not be the result of lower reliability.
Factory offerings are generally a good compromise, but a compromise is not usually exactly what you want.