I have done all ends of this over my years. One of my guild elected to stay on server and attempt to merge there with another guild, another one elected to stay on server and try to recruit and my current one elected to server xfer to a better realm.
All the reasons for an "action" were the same. We couldn't keep getting good enough people to progress the way each guild wanted. I can tell you that xfering in my most recent guild is what saved us and made us better.
Picking a server was an interesting issue due to how many people want a server in a cluster closer to them for lower ms. In the end, you just need to pick one that fits your guilds needs. In our case, we picked a server with some close on server competition in hopes to push players more to do better, it worked well. If you are going for something similar, you'd need to do good guild research on where you are going. You don't want to go to a server that has lots of guilds that raid the same times as you but are distinctly better in progression because that would mean you will have trouble recruiting as you are the "2nd" guild in that time slot etc.
The biggest thing is make sure the move actually will fix your issues. Don't just xfer because you are having troubles and want something new to hope that it fixes everything. Make sure that it is ONLY a recruitment issue you are trying to fix. Nothing will kill a guild faster than xfering in a bad condition.
It worked out well, recruitment opened up hugely, the new server got some life back in to people cause they could actually go and do things instead of just afking in towns and the economy was hugely more useful to us.