I would recommend checking your rotor and stator windings on any ST head to make sure that they are copper. If aluminum, consider the boat anchor application unless it is for a show piece where long term reliability is of no concern.
The only thing going for ST's is the price, and the lack of other choices until over triple the price for 4 pole, 1800 rpm head in the 3-5KW range. The variation between different units, even from CGG, is dismaying and includes the use of aluminum on rotor windings, huge variation in Z winding output, failures of Z windings. Winding failure on copper windings suggests the use of substandard insulation. I'll know more when I've done some testing with a new mega ohm meter.
For the larger heads, Gary of DES has recommended the Stamford clones as being a good, reliable choice. I would take his technical advice to the bank, myself.