1" or 1.4" driver ?

I presently use an Altec 806 driver on the Stereo Lab Tractrix 400 Hz round horn. The horn has a 1.4" throat and I use it with an adapter (Paudio I think). The range covered is 800-6500 Hz with 24 dB LR slopes. When properly tamed in the 2- 3 kHz region with parametric equalization it sounds quite decent or even good, who really knows? In any case better than Klipsch Cornwall and the same driver on a 511 horn.
Then the usual audiophilisis strikes, would it sound better with a real 1.4" driver? I have searched and read a lot of forums but didn't found a lot of clues. I'm thinking about Radian 745 or GPA 399 since I prefer aluminum diaphragms.
Can anybody explain the aim of 1.4"drivers and difference between the 1 and 1.4" drivers? more power, lower cut off?
Does the sonic difference be perceptible?
Apart of the exit angle of the driver/adaptor /horn issue are others other issues to consider?
Of course the obvious recommendation is to try but it is not a trivial task and it cost some hundreds.
Any opinion or help is welcome.
Chris

You will have to provide more info as to woofer type and what type of box using.
Is it for home use?

I've worked with both the A-7 and A-5 .

For films A-5 is much superior and does not clip. 1.4 "
Well suited for lively halls where acoustics is a problem.

For CD music with a McIntosh amp very impressive.1.4 "

The model 19 is also outstadindg. 1"

For live studio recording the 9845 is outstanding.1 "

The 604 8G is also outstanding with Master tapes.1 "

The 1" throat seems to have problems with 35 mm Films with clipping.

i have the same horn from stereo lab, the 1.4" large format drivers sounds better, a lot better. i have tried altec 288 K, H, G and 290L in this horn and i like the sound of the 290L the most. it has a rich, smooth, mid range tone. the thing is with altec 290 with 400hz tractrix horn the frequency response is only flat from about 630hz to 6xxx hz. you will need an upper mid driver or a tweeter that can go down to at least 6000hz to make the 290 work properly. otherwise just use a 288 driver since you like aluminum diaphragms .

Although it is my opinion the 1.4" Altec driver has more fullness and body when compared to the 1", the primary reason that I specify large format compression drivers is because they can get louder without noticeable distortion.

Guys thank you for the replays.
To respond for the request of one of you. This is for home hifi use. Until know I never had problem with power even with the 806 at levels around 100 dB at the horn.
For information I use JBL2235 in bass reflex box from 35 to 140. then 414-A in open baffle to the 400Hz horns and a Beyma Cp-21 slot (near copy of the JBL 075 tweeter).

The tweeter hardly goes down to 7 kHz so I need a driver which goes higher than the 290 series (300-7 kHz ? 10dB and phenolic diaphragm). The 288 could do but at very high price ticket. That's why I was looking at the Radian(226$)or GPA (340$) drivers.

May I resume that 1,4*in. driver can play louder and what ? do midrange better than 1* inch ie fulness and tone, is that right?

Onextwo have you tried some 1 in driver on your horn? Do you have some measurements?

These might make the choice easier:

http://www.jblpro.com/pages/pub/components/2404.pdf

Cheers, Marshall.