What kind of server is preferred?

I will try to make this story as short as possible. Basically, my husband and I moved our main server from a vps to dedicated server, with more stability and incredibly reduced lag. We still have the old vps server up for another week and half so he just made it into a 100% vanilla survival hardmode 1.7 server. We are getting more people joining the old server then the main one. Granted our main server is still 1.6.4 because we are waiting on craftbukkit to update, but it offers 4 different survival worlds, several creative worlds...just to name a few neat things about it. So do people want more of a vanilla, straight out of the box style server or one with mods on it? We have been promoting the heck out of our main server and we can't seem to get more people on it. We have put months of work into our main server, including the builds with our admins and moderators. What is it that people want more out of a multiplayer server? What else can we do to promote it and get more people on it? We throughly enjoy chatting and playing Minecraft with others, hence forth why we decided to make one months ago. It is a struggle to get the word out there about it. Any suggestions would be greatly appreciated, thank you!

If anyone wants to check it out its
minecraft.slak.pw
its called Slakers Paradise