Is the 2014 sl550 really faster than the 2011 sl63 amg

Very close, 550 has more torque, 63 has more horses, if there is any difference in performance it would be relatively insignificant (owned 2009 SL63, rented current SL550 in LA on numerous occasions).

 

I have the SL63 with the 6.2 and the SL550 might have more torque and perhaps a click faster- but the 550 in my car's chassis was so softly sprung and shocked and braked that I can't imagine it could do much with a few more foot-pounds...

But I haven't driven the '14 yet.

 

My dad has a new SL550 and I toyed with the idea of buying the previous-gen SL63 before the Ferrari.

The SL550 is definitely a bit quicker off the line thanks to the turbos. At full click through a few gears both cars should be evenly matched as the SL63 has more topend and quicker shifts. Both run about mid 12's stock. A Renntech tune will turn a stock SL550 into a 530 horse and 600 ft lbs of torque beast though with no other modifications.

I don't know about costing less since the 2011 SL63 is in the $70k-$80k range, while a new SL550 is about $110k with decent options.

 

I had an 09 sl 63 . It was fast and throaty . Now I have the 2013 new body sl 63 twin turbo and it takes a moment for the turbos to kick in . The new design is ok but the new interior is stunning . I really love the car . My advice is to buy a used 13 or newer 63 as these cars drop like a rock but a lot of fun to drive in sport + mode . Good luck.

 

My 13 also has the Kleeman chip cost + - 2500. Money well spent

 

Best advice here.
The new 63TT is a monster of an engine, with Renntech tune, intercooler upgrade, downpipes and exhaust in my daily driver E63 S it shows 622HP at the wheels.
Very tunable and bulletproof powertrain, performance is just mind boggling for a family sedan.
It feels like a really fast bike in acceleration.