Loco15666,
Hi, the main advantage of tender driven model locomotives is that more detail can be added to the loco including light under the boiler etc. The larger more powerful motor can be more easily hidden in the tender. Hornby often added traction
tyres to the tender wheels enabling longer trains to be handled. I have had no problems with OO tender driven engines but remember that the newer similar engine driven locos will have newer and hence 'better' motors and detail.
Have fun.