Unfair co-first authorship I am a PhD student in chemistry and my funding is specific for a certain project. This funding also funds another PhD student, a biochemist, with a different advisor (both our advisors are very well-respected). We're both in the 3rd year of our PhDs. 

The project is now in its sixth year. The distribution of work is as follows:


Some post-docs had done the first 4 years of this work
The other student provides the animal samples and some biochemical test
I do the "novel test". This test is labour-intensive and time consuming. I very often work on holidays, while the other student doesn't even answer mail after hours, despite having a technician to help her. 


The problem is the papers. We are now going to start our third sub-project on this work:


Paper #1 [last year] was primarily the post-docs work, with authoring PostDoc*, OtherStudent* (where * denotes equal contribution)
Paper #2 [last year] was mostly my work, with authoring me*, OtherStudent*. I was extremely heart-broken and wanted to quit, but my advisor assured me that this would not happen again
Paper #3 [this year] is the problem. The other student sent a new batch of samples in for a new paper. My advisor said that it is very likely that the other group will ask a paper co-first authored as: OtherStudent*, Me*, since the other student had not been in the first position of the co-first-authorship yet. 


I believe it is unfair that I have fewer papers than this other student despite doing much more work. Indeed, this other student has time to work on other things and get still more papers published, where I am working flat-out on this effort.

My advisor and I argued and I told him that I want to switch to a different project, but he said I can't because my funding is specific to this project. I'm thinking to quit and apply for a new PhD somewhere else but I have spent 2 years and 2 months in my PhD and I believe I will also have problems in the new place (hopefully not as bad). 

Am I right to be angry? How should I approach this situation? 
How do people in academia actually look at co-first authorship? Is the order important?
Maybe a workaround would be to explicitly assign credit in the paper. This seems to be used in some disciplines and I think it makes a lot of sense, especially in an interdisciplinary project where customs about authors order might differ. 

It simply consists in a footnote at the beginning of the paper or a section at the end where all the authors are listed and their contribution is summarized, e.g.:


A conducted experiment X
B collected Z for experiments X and Y, prepared Z and conducted experiment Y  
C proposed the approach and designed experiments X and Z
D proofread the paper
...


In my domain I'm not very familiar with this usage, but I've seen it in a couple of papers (in medicine as far as I remember). 

This could be a way for you to avoid a serious conflict in the project, while making clear to any reader which author did what.