First thing to answer is if you need dual extrusion y/n.
If not an ultimaker is superb! Lightweight head and easy to maintain (you can repair it yourself if you how to use a screwdriver) and you have the support of this forum.
If you are not in a hurry ultimaker might someday also have dual extrusion. If you want dual extrusion now you can have a look at the BCN3D sigma. A Barcelona based open source printer.
whatever you do buy open source. .. the availability of all info you need and the ability too upgrade parts is something more important than you might realise.
And depending on where you are go visit a shop. In de Netherlands f.e. I like Makerpoint (arnhem is closed for me).
3dhubs.com has the best printer comparison information. I strongly recommend them - it's pretty easy to find from their main web page - only one hover and one click. (start with "learn" menu).
dual extrusion only on the UMO. Not sure that UM2 is any better than UMO+. Both printers have had lots of advances - UM keeps improving both of them. To see the kind of quality you can get go to this thread and be prepared to be blown away:
Start with this page and go backwards - only looking at pictures until you see something you like:
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