I've been using Lr/ACR for landscape merges recently because dcraw hadn't been updated in a long time to deal with new cameras. Now that it has..
OMFG.
It stitched a 21 image preview in less time that it takes to start Lr or Ps! (j'king)
It completed the merge so quickly that I thought it had failed.
With Lr I would have gone for coffee and then probably come back to some sort of error.
Damn these guys are good!
Sigh... I have been saying that for about 7-8 years...
Jokes aside, glad you have tried, PTGui is totally outstanding indeed and leagues ahead of PS and LR. So much better it isn't even funny.
I can't even think of a good car comparison because PTGUI would have both the convenience of the Golf, the price of a Skoda, the quality of support of Bugatti and the performance of the Ferrari. Its only downside is complexity I guess. It is a tool for dedicated stitcher not the occasional user.
The only alternative is Autopano.
Cheers,
Bernard