Wondering about best method for patio construction. Which is more stable and resistant to movement/settling: a poured concrete base OR a crushed gravel bed base? Thinking of a 700 sq ft patio (20' x 35'); 2 sides of patio will be immediately adjacent to house structure/foundation; area covered by patio has a natural grade drop to one side of about 1 foot over 20 lineal feet; concern about water and drainage on the property lot so want to build most stable structure to prevent potential negative settling issues from water or grade ; either way I will be installing substantial drainage solutions to direct water off property and away from patio; patio finish surface material may be pavers/stone/brick or perhaps just concrete. Please help me understand advantages/disadvantages using either base material and what additional steps can be taken to make a long term stable patio (ex. use of retaining wall with gravel bed, pouring sub frost-line footings for concrete, etc.). Thanks!