I think it depends on who's rowing the stick.You certainly can dish out alot of abuse to the whole powertrain if you don,t use a little common sense.Myself I think the manual tranny is the way to go.Did you know it takes horsepower just to operate an automatic .Remember when the 5.0 mustangs really became popular in the mid to late 80s the 5 speeeds were much quicker than the automatics because they had more horses getting to the ground. You also can launch at whatever rpm you want without having to have a perfectly matched torque converter for your combination.Change your cam or your gears, you'll probably need a different converter.Shift at whatever rpm you want and as fast or slow as you want. Sticks launch much harder and this is probably where your opinion of them being hard on parts comes in.You have to keep in mind how strong the rest of your driveline is before you sidestep that clutch at 7 grand! Thats where the common sense part comes in.I also believe a rev limiter is a must to protect the engine from the occasional missed shift. Automatics can be built to work very well and are very consistant for bracket racing but they are also expensive to build especially if you are swapping convertors and stuff all the time.If you compare the topics in this forum most of the ones about automatics are questions about what convertor to use ,what shift kit how do i run the lines , keep it cool,etc.Most of the questions about manual trannies are what do I need to get one in my car!Theirs nothing like dropping the clutch and hammering through the gears.I know they're not for everyone and Im sure lots of people will disagree with me but they definitely have a lot of good points.
One area where the manual can be "harder" on the engine that the auto is when you release the clutch, the pressure forces the flywheel forward. This causes the crank to move forward. Your crank, main, rod clearances must be correct to avoid problems.