Well as Michael noted we can only do our best being a small company. Most companies would have retired the product were as we choose to keep developing it. I think we have done alot of work with vbGallery and added alot of features over the years especially remembering the 1.0 code base we started with. The code base we started with had lots of unresolved issues that we had to fix and lots of new additions since then and I know the 3.0 code base for vb
4 series alot of work was done with that to support vbulletin4. That was essentially a complete rewrite of the code.
Does vbGallery have all the features of Pro no, however take into account that Pro is alot more mature of a product having been in existence about twice as long as vbGallery.
We have had a vbGallery to Pro import script available for along time. It is available for download in the PhotoPost Pro import script forum here. Photopost vbGallery to Photopost Pro Import Script
There is nothing we can do about your urls in posts with any absolute certainty here because these are two separate products with different url formats and even different file structures. We have no control over links placed in outside applications. However if you do decide to switch based on your example urls above there is a query you can use that might switch your links if they are as you are posting above. You would need to backup any database and my example would change any links based on your direct example but its a powerful query something we do not directly support since this has nothing to do with our coding.
UPDATE post SET pagetext = REPLACE(pagetext, 'vbg/showimage.php?i','gallery/showphoto.php?photo');
Now look at the query basically what it is going to do is find any reference in your forum posts of that portion of wording and change it the second part which should make the links work. There is nothing I can post that is going to help you with direct file structure links in posts. Hope that helps
Personally I like all the work we put into PP8 and I think you would like it. You are permitted a test install if you lock it down via htaccess so it is not web accessible to the public. You could do a test import of vbgallery using the script I noted above. You could then see if the new Pro 8 is to your liking and decide if you want to switch. If so then you could make it permanent and do the database query I noted to try and change post links to your new Pro install.