this statement is actually completely wrong,
It is completely irrelevent wether or not a book deals -105, -110, or even -120.
What is relevent is wether or not that book has the BEST AVAILABLE LINE on a semi-regular amount of time. Or wether they have certain +EV betting options that are not available elsewhere.
SIA is a -110 shop, but they are damn solid in terms of payouts and often have the BEST AVAILABLE LINE on a given game, several times a day. Matchbook may have +104 on a game, but if SIA has +110 that is all that counts isnt it?
BET365 is one of the most stable shops on the planet, they deal -110 but they often have THE BEST AVAILABLE LINE, especially on underdogs.
I can go on and on with examples, GREEK, CRIS, WSEX are invaluable for their early lines, bettors who took Daniel Day lewis at even money to -400 were laughing by the time other books came out with the same line at -1500.
Other books are good for their In betting options, Their contests, their customer service.
It might be a fair statement to say (like trytrytry said above) that you will play less, at certain books, but if you are semi serious about making money, not having these types of places funded with the mentality that "lay -110 shops are useless" is a complete fallacy. Even if only 5% of your plays go through a particular -110 shop, that 5% is still important for your overall arsenal.
EVEN D rated books have a certain roll in your arsenal due to the value you can often extract from them, what is extremly important is that you do not over expose the portion of your bankroll with them, perhaps 5% of bankroll maximum with these books.....
Once you are loaded up all around, you are then ready to get the best line.