Mcj- my preference would be to not invest in a co-op for the simple reason you are not in control. The board may decide to make an upgrade, hire a non-insured contractor or any number of things that could result in liability for the building owners (you included) and an assesment you cannot pay.
One example is a roof, many home inspectors or contractors may say it needs to be replaced ASAP when in-fact it can wait another year or three. As a sole owner, you decide when to make the investment of capital improvements but in a co-op the board or members al large do depending on the organizing document rules.
In addition, in my experience they don't have the same resale value and most cities discourage them because if owners rent units it becomes a nightmare. The city has to contact some 100 absentee owners instead of one when an issue arises.