It's an interesting problem as to which system is best, it is very subjective.
The factors involved include looks, strength, reliability, etc
.
One of the down sides of the Dingham is they are 'handed', ie all stock
has to be facing the same way, but they are quite discreet and reliable.
[if you think they are difficult to assemble, you should try the 4mm ones!]
S & W are certainly effective in 4mm, [haven't tried 7mm] and can look good.
If you go down the T/L route I'm assuming that you will do the Brian Kirby
mod and use magnets.
The other option is Kadee, but in my opinion they don't look right on wagons,
ok on coaches. Then you have the problem of different couplings for each
type of loco [freight or passenger].
I did see an article on a clever system using an eccentric on the axles which
allowed you to uncouple anywhere by simply giving the coupling some slack,
this allowed it to work where ever it took your fancy!
Of course, there will eventually be a DCC auto system, it all depends on your
timescale and budget.
Good luck, Jeff