Hand signals at 3.5 are awesome. Much better than a verbal conference. Since use of signals is so rare at that level, some opponents will wig out and miss because they are so worried about the signaling.
Alas, I haven't been able to use them much. When I am serving, my partners don't want to signal because they don't like (or can't) poach. When they are serving, they don't want the additional distraction of having to remember whether they must cross.
The one lady who is a big fan of poaching is injured, so we haven't had a chance to play together. I hope she gets well soon . . .
I have never seen signaled poaches at 4.0. I think part of the problem with signaled or planned poaches at 3.5 and 4.0 is that the serves are often weaker than the returns. Having a planned poach will require the poacher to handle some pretty hot returns.
Oh, and verbal conferences between points are really annoying and inefficient. We play timed matches, and a lot of these conferences go too long. And of course, having a verbal conference doesn't strike fear into the hearts of opponents the way a signaled poach does.
I wouldn't say one is better than the other as it's a personal preference thing. Some people like signals, some like to talk.
IMHO - I prefer to confer with my partner, that way I'm not wondering if he saw my signal and it's less of a distraction during serve since I already know what the plan is when me or my partner step up to the line to serve.
In addition it provides a good time to mention any observations or change up strategies without being obvious. If the other team hasn't talked for three games straight then all a sudden they meet up out of no where, you know they are going to try something.
As for time, it's not a conversation for the most part. My partner tells me where he plans to put the serve (wide, body, T) and I'll usually poach based on location. If I plan to poach, when it's not expected I'll let him or her know I'm going. - Only takes about 10 seconds max.
Granted, there's only 1 or 2 people that I've played with enough during the season that we could make talking or signaling work very well. Even if we don't signal, at the very least, if I'm going to poach, I'm going to tell my partner so they know what to expect.
Also - IMHO - a fair number of mens 4.0's do have a big enough serve to cause a weak return. I think the biggest reason why you don't see alot of signals, etc. is that alot of times your partners change, so it's really hard to be familar enough with their game to make it work well.