Well, I'll bite, too. In retrospect, I guess my intial reaction was due
to a coincidence of two irritating moments:
(1) A shameless plug from a dealer for a certain plane, with absolutely
no valuable information at all. It could have been an ETA, a Duo
Discus, an ASH-25 or whatever, and I would still have criticised the
original post as the covert advertisement it is.
(2) The shameless plug actually promoted a PW-5/6, which in my very
humble opinion (though shared by many others) is a couple of
offensively ugly gliders. This probably made my initial statement a bit
more "spicy" than necessary. ;-)

Answering your question, I would recommend a combination of ASK-21 and
LS-4, both quite versatile gliders, usable for teaching but also in
competitions.

And no, these are not the only gliders I have flown in my life. And
yes, these are the gliders I have been trained on, and I still think it
was an excellent choice of our gliding club to transition from BF
III/IV + K8.

For XC-teaching we have come to use Duo Discus, which for the student
is the 2nd two seater glider he/she will learn to fly. The Duo is of
course far superior for XC than the ASK-21 and at the same time offers
the student the possibility to hone his/her gliding skills: Starting
and landning is less easy than ASK-21, but the reward is far better
performance.