a 5 speed or a 4 speed are not going to be able to handle horsepower
any differently then each other. thats a load
the strength of the tranny has more to do with the tranny case,
the differential, the ring and pinion and all the other internal pieces
inside. For instance... I 3.88 R&P is going to be stronger then a 4.12
or 4.37 VW R&P. A Super Beetle Mainshaft is stronger then regular
beetle Mainshafts. Aftermarket gears are going to be stronger then
stock gears...
The reason one would choose a 5 speed over a 4 speed it to be at the
right RPM range thru every gear, plus have a 5th gear for overdrive. The main
downside to having a 4 speed is that you have to space all 4 gears very
far apart so that you can attain high speeds. This means you will be in each
gear for a longer period of time then a properly geared 5 speed which
will equate to a less then efficient situation do to the fact that you are
not really staying in the proper RPM ranges with the 4 speed equating to
slower 0-60 times, 1/4 mile times and accerlation times.
I have owned a 914 with a 1.7 Type 5 and 901 5 speed and let me tell you
that it is an excellent tranny for a Type 4. Once you get used to the shift
pattern, it is a very fun car to drive. One word of caution, the 901 is not
a drag racing tranny. It is setup for track racing and autocross do to the
dogleg pattern.