I've heard millions of times(on these boards) that in FX Daily, 4HR and 60MIN are the TF of choice for the banks. maybe its true, maybe its not.. but TF's should surely be chosen for their characteristics and how they fit into your personality/style I don't think cost/account size is a good enough reason these days(we can all find a broker that allows flexible/mini lot sizes)
As for ...
1) overnight risk.
Information comes in all day every day, disasters happen sure but most news is scheduled. Most action happens London/NY sessions and out of these often little or no movement occurs.
2) overnight margin.
I'm assuming your talking futures as I'm not aware of an overnight margin differing to margin
3) financing cost
Most have a daily rollover, some don't. O+A charge interest by the second... is that good? or bad?. Good if you only trade with the carry. Long term trades like long cable, short euro would both pay interest as well as the pips. Since they typically move together choose one when a long shows itself and the other when a short turns up if it bothers you.
4) economic news
If your looking for big pips on trades lasting 3 days then news is unlikely to concern you unless opening a new postion. As someone stated I would imaging using the 4hr more often than not the news will confirm you postion.
longer....
less noise, fewer trades, less volitility, bigger moves, smaller costs,?bigger stops?, candles more meaningful, S/R more weight?
shorter...
more trades(less daily variation of P/L?), more volitility, higher costs,smaller moves?, stops.
each TF has its own noise, volitility, followers and trades... for each good reason theres one for another TF so its got to match your style.
(Ps: one last thing, how come the 60 min looks just like the 4HR if you scrunch all the bars up
The noise seems less important