MTB or S-Boat, which would you command?

Of course there were many motorcraft used in the war, but most of them fell into two broad categories. PTs and many MTBs and MGBs such as the Vosper type were 70-80 feet long. S-boats and the Fairmile MTBs were a bit over 100' and 100 tons displacement. There were also smaller types like the MAS or Japanese boats with just a couple of torpedos and machine guns.

Naturally the smaller boats tended to be less heavily armed, but the American PTs made an important change in mid-war, replacing torpedos in tubes with Mk13s, originally aircraft torpedos, which only needed light racks. This freed up a lot of weight for heavier guns, up to 40mm, plus things like rocket launchers. This type PT had an armament comparable or even superior to an S-boat.

The Fairmile Type D MTB could carry a heavy gun battery including Molins automatic 6pdrs in addition to torpedos, combining the roles of MTB and MGB. The most heavily armed "Dog boats" outgunned the S-boats, with one caveat, I believe the 6pdrs were low-angle only. Also the Fairmiles' torpedos were 18" while the Germans had 21".

The S-boats were the only I am aware of having much armor, particularly around the bridge, the so-called panzerkulotte.

The S-boats' big advantages were in sustained speed, range, and seakeeping, which at times can be more important than the sexier things like guns. So the choice to some extent depends on where you're operating and exactly what you're doing.

 

Seaeeping capabilitity is critical, the small MAS,that had been fairly effective in the Adriatic in WW1, proved unsuitable for the central Mediterraneran. For gun armament the stability of the platform counted as much if not more than the number of guns, and the bigger boats had a definite advantage there.

 

My scout master form boy scouts had been in PT boats during the war. One of the boats he was on was sunk but due to a storm and not enemy action. Sea keeping is indeed important.

 

Not the old S-Boats but east german S-Boats at 50 knots. the footing give some impression of speed
https://www.youtube.com/watch?v=crLWvlv2BEg

 

My late father served on MTBs in WW2, he was on one of the boats which were sent out to intercept the Brest Squadron when they forced the Channel in Feb. 1942 ( "Operation Cerberus") and was part of the naval force which took the paratroopers off the beach at Bruneval two weeks later.
He rarely spoke about his experiences unless he felt the need to, he told me that some of the most fearful moments he had were "lying off Texel" waiting to ambush "E Boats" returning to base.
He said their diesel sounded different and if action was joined it was a fast close-quarters battle with nothing held back, often a running battle - the S Boats he found to be faster, heavier armed, and with better sea keeping qualities.
"Our boats" not as fast and prone to fire and explosion of fuel tanks.
Seaforth Publishing has reprinted and updated a two-book set on Allied Motor Torpedo and Motor Gun Boats a great set of reference books that has very varied and comprehensive photographic coverage and excellent line diagrams for all the makes and variations of MTBs and MGBs both British and US.