can somebody tell me why should I choice UBB and not IPB or vB ?

only you can decide that to be honest.

I'm happy with it

by testing different forums , I like UBBs structure , but I think vB is more stable ... is that true ?

I think he is looking for more of a list of PROS vs. CONS between them.

I'll leave that to someone like Gizmo or Rick

Yes I too like UBBT enough that I bought it.

exactly

This is a very subjective question, so it makes it a bit hard to answer. We've never done comparison charts against other software, because honestly, comparison charts usually misrepresent the competition, unless you are extremely familiar with their software.

So, honestly, I can't say why it's better than VB or IPB, since I don't know much about either product.

As for stability. We're just about 10 years old and we have a pretty large customer base, so I don't really think stability is an issue.

I could rattle off some of our features, but you'll find that on our feature list page, minus the new stuff in this version like the built-in gallery.

As you can see, I'm not a sales person, just the developer. We try and focus more on what our existing customers want/need rather than what will attract new customers in mass. So, that is one of our PROs I guess is that we really try to listen to our current customer base and what they want.

the best feature Ilike of UBB is then when you have a new post reply , and you click on the topic it sends you directly to the new post , and not to the page as IPB and vB

maybe you should put that features in the list

Both products have very robust features. When you step back from all of the features, there is the general, overall look of the forum. No matter how much you customize each kind of board, you can usually tell the difference when you first visit a board. I like the look of Threads over VB.

Ease of use overall. I participate on a couple other boards that are not UBBT and they work okay but are not as easy overall and esthetically pleasing as UBBT

The other boards do not have an easy if at all way to ever converse with someone actually doing the coding. You can talk to people that are Tech Support in the forum and they will "pass the information along" - (yeah right), but here you can actually get a response typically in a very short time from the developer.

That alone is a BIG difference worth it to myself and many. It gives you more of a feeling of (I belong to a group that does want to share and help each other rather than I'm just a customer).

Why is UBB better than vBulletin? Have you read their faq; vBulletin was initially based off of the UBB, it states it in plain text... Now, obviously infopop was doing something right if they had to do a php port of UBB.Classic to sell to customers...

Plenty of companies have done something similar either from UBB.Classic or UBB.threads and now run fairly popular forum titles, but if you get down to the nitty gritty, a part of the UBB can be found in their core; it is UBBCode for a reason ya know...

Why the UBB?
Caching
Quick Reply
Excellent developer who LISTENS to his customers and is extremely helpful
Friendly member base
CSS Styling System
AJAX functionality
Gallery forums
Non-encoded source (Some forum titles encode their php sourcecode in either IonCube or Zend; evidently they don't want people stealing their work that they stole elsewhere lol)
Upcoming permission system enhancements (slated for 7.3)
Upcoming payment system (slated for 7.3)
Upcoming video blogging options (slated for 7.3; a mod for this can be found over at UBBDev anytime)

I could probably go on for hours