P gargantua has large, 2" plus flowers which are deep red except the dorsal lip which is paler, a little 'washed out'. Usually there is one flower per leaf some leaves have 2, I have never seen 3. Andy says he has seen them with uniform deep red and as many as 3 flowers per leaf, my plant which has 50 odd leaves and has bloomed many times has never done this. The bloom pattern is sequential, this spring it will have from 20 to 30 flowers spread over 3 month, I have never seen more than 3 at the same time in bloom. Some people like that as there is a flower present over a long period of time, I prefer them to make a flush of flowers as it is much more spectacular.

Summing up:
Large flowers
Pale dorsal lip
Max of 2 flowers per leaf
Sequential bloomer
This is a spectacular plant and I'm not knocking it, the disadvantages are only described for the purpose of this thread.

PLEUROTHALLIS TEAGUEI is also a great plant, out of bloom looks similar to the above. It's a warm grower, the above blooms cold. The flowers are about 1/3 in size but it makes 7 to 10 per leaf. The color is a deep purple and the blooming pattern is more of a flush where the vast majority of flowers appear at the same time.

Summing up:
Flush bloomer
Smaller flowers
Deeper color
Many flowers per leaf.

PLEUROTHALLIS BEV DEBRINCANT. I have 2 plants of the cross, had one in the cold house and one in the warm house. The warm one is doing much better, both are now growing warm. This spring the larger of the 2 really demonstrated what this plant can do. It's still young with only 5 large leaves but they are all in bud/bloom at the same time so it appears to be a flush bloomer. The flowers are similar to the gargantua in size and shape but a much deeper uniform color. One leaf has 7 flowers, all the huge flower size and shape of gargantua.

Summing up:
Flush bloomer
Deep uniform color
Large flowers
Multiple flowers per leaf

To me, this hybrid truly picked the best feature of both parents. Obviously you want this anytime you hybridize but it is not always achieved in such a spectacular fashion.

Nick