When I started TKD 5 years ago, we were taught Palgwe poomsae as color belts. Apparently palgwe was the form used for tkd up until 1968ish, when the taeguk poomsae was officially adopted/endorsed by kukkiwon.
That being said, my GM came to US in 1968, so it makes sense that he thinks palgwe is a better form for beginners. During palgwe training, we were taught to make very wide long stances for maximum stability, and a lot of wait rotation to maximize power. The forms also had many "round" motions.
Then after you attained your 1st dan, you were taught taeguk poomsar, along with goryeo.
I was very confused as a color belt. This is because there was a master from our school who was on the US National team. She would pull me aside and tell me to not make my stances so wide, and less of the over pronounced "core" motions when doing blocks. This was in contrast to what the instructors and the GM were telling me.
My master(as we were a secondary school of GM's)who was the headmaster of our dojang, and who is KTA trained, told me that the old palgwe poomsae advocated stability and power.
After 1972, the KKW/WTF decided to sacrifice stability and power for agility and speed. So for the taeguk poomsae, I was told that the long stances are narrower (whereas a real palgwe long stances are wider). Also for taeguk poomsae, the motions are more linear and fast.
On my personal opinion, I think there are merits of both forms. As I am not going to be sparring at my age (mid 40's), I think working on power seems important as it seems appropriate for kyukpa (breaking). But I am happy to know that not all long stances are (should be) the same.
Same goes for kicks. An assistant instructor that came and went in my dojang convinced everyone that there is only one roundhouse, where you flick your leg back as fast as you hit your target (or you get your leg "grabbed"). Obviously this made it so much harder for the poor color belts to try to break boards. My master explained to us that there are multiple variations of kicks (kyukpa, deminstration, and sparring versions just to name a few) roundhouse inclusive.
These things being said, I feel that palgwe and taeguk have two different approaches to tkd, one not being superior to other (in my opinion).
Like most people, I am glad that I found TLD, albeit late in my life.