From an admin perspective, XenForo is far easier to use and less of a hassle than vBulletin or any other forum software.
From an end user perspective, it's much more modern looking than vBulletin. IP.Board is a close second if used with a good theme but I've never administered an IP.Board forum so I have no idea if it's really any good.
It seems like people keep mentioning photos and galleries as the big sticking point on this site. More than one person complained about it -why doesn't the forum administration do something about it?
The reason I don't think Tapatalk is good is because it's so, so annoying for people that don't have Tapatalk, especially on mobile. Also, like somebody mentioned, it's a very proprietary solution that takes away control from the forum owners.
In terms of the donations page and premium memberships, it's completely half assed and doesn't explain why you should. Money doesn't grow on trees and I'm not going to drop $25 to 125 with no explanation of what I'm getting.
There are many active members here that are here because they are passionate about their trucks. There's also many people that don't really care all that much and just want tech support and once they get that, they will leave. Those members are never going to donate - you need to cater to the active members who stick around, and give them a reason to upgrade to the premium memberships.
If that means introducing a great new gallery system and maybe even spending money on a XenForo plugin that does that well, do it.
As far as revenue, currently there are Google AdSense banner ads. A great first step, but there are more options. VigLink will help you make money using affiliate links when people click on links to products on Amazon and many other retailers, and it doesn't cost the end user anything or inconvenience them at all. Also, InfoLinks does in-text pop ups which are pretty annoying, so maybe only display it for unregistered members, but it does pay well. A big banner to register to get rid of those annoying ads might get more people who just need help to their questions to register. Would they stick around? I don't know.
Also, I do agree there are many extraneous categories. Less categories will make the forum appear bigger. For example, all the for sale categories could be combined, you could combine the "Games" forum into "Off topic discussion". "Site support" could be merged into "Comments or suggestions" and just call it "support and community feedback" or something. You could Otherwise, just look at all the categories that have less than a dozen threads. Big problem and easy to fix, too

a big offender is the "Traverse, Acadia, Outlook, & Enclave" section. There are less than 20 threads in the whole category. Make that one subforum.
Final thought for now (I have to go somewhere) do we have a truck of the month? I think most other truck forums have this... where people can submit a picture of their truck and members can vote each month for "truck of the month" and then display that somewhere. That way the best looking, coolest modded, or even cleanest stock examples of the vehicles we discuss will be displayed.