What you choose is very important and affects how you will be paid.
With the cash upfront payment, you submit items for editorial consideration, this is then either accepted and a cash offer made or rejected for several reasons.
Yahoo! will turn down your work for several reasons, especially if the work is time sensitive such as news or sport based. Editorial consideration can take two or three weeks so you need to consider if you really need the two or three dollars quite so soon.
If you do want to sell your work outright, it appears, in my experience, that items sold for cash then never receive any performance payments. You only get the sun that was offered in the first place.
From my calculations performance payments or CPM (cost per thousand) in the first few months on Yahoo! Contributor Network receive a payment of about 1 cent per 5 or 6 views. so it can take a while for your cash to build if this is your main means of income from writing on the site. They pay out when your performance views reach about 1,500 views. ($1.50) In the early stages you get less cash per view than later as you get closer to 1,500 your payments are supposed to increase.
Taking cash if you can in the early stages seems to make sense if you can, but if you want to use those items to increase your CPM payments then maybe if they are good subjects that you are certain will bring in readers over time you may be better off foregoing the upfront payment and the editorial delays and opting for performance payments only. This means your work if you publish immediately for performance payment is available to readers for anything up to four weeks sooner than it would be if submitted for editorial review.
If it is a popular item you could have 2-300 views in that time if the item is well publicized.
That way as time passes your work will continue to contribute to your income for the longer term.
As you write more items your required number of CPM views actually falls, so one item requires 1,500 views to pay out. 100 items only require 15 views per item on aveage to reach the payout level.
Believe you me, the level of 15 page views per day is very achievable above the 50 items posted level.
This is something well worthwhile in considering as you look into making cash from your writing.