Both jpm and ubs don't have retail banking in sg so my exp with them is on the PB side. I would say I prefer jpm as their style fits mine the most and I work with a great team. They are very proactive in investment ideas but not pushy. What I like best is that they take the time to explain each products with pros and cons and the result is that I get the confidence to make a decision. It was especially important for a finance dummy that I was.

I have learnt a lot from them.
They offer access to all the usual bonds, equities, derivatives, fx and PE funds. Some other banks can't provide. They also gave me the highest ROI among all the banks. Their rates are the best in terms of leverages in various currencies and fees are the most attractive so far. However, it really depends on how much AUM you have with them when it comes to rates. The more you have, the better rates you get. Also your experience depends on the RM and analyst team you get. Their team is one RM supported by a few analysts.
As for UBS, I have less history with them but their style is very different from jpm. A lot more conservative feel and maybe it's because of my RMs, they are less proactive. They don't give you direct access to their analysts. All must go through rm. The rates for loans are not very attractive which limits my exposure to non sgd products so not very good. ROI is too early to tell. Product range wise, similar to jpm.
If you are keen on some special credit cards, jpm and UBS don't provide because they don't have retail banking license in sg.