I would definitely go with the 2 Type R 12's myself. Not only have I personally seen the Type R's out perform the L7's many times but two 12's will push more air than one 15 and therefore have higher SPL levels. However as for money, obviously one L7 will cost less than two Type R's.
I personally would go with two 12"s but it really depends on what amp your using and what encloser. The 15" would hit the lows better but the 12"s will have a wider range.