*Disclaimer: What follows is a post about structural biases I've perceived within the NSF Biology system. I think these biases are intrinsic but keep in mind I could be completely wrong (and if you have different views, please feel free to comment). They also aren't inherently bad or need to be fixed, they just exist based on the pool of reviewers/panelists and timing of the grant cycles. It's a bit rambling, but I'm hoping to provide at least a slightly useful insight or two.
Even before the new office smell has worn off, and in many cases before you've actually moved into your office, the thoughts of many PIs newly merging onto the tenure track are focused on grant writing. This isn't going to be a post about how to get NSF grants, but more along the lines of "things I've experienced writing grants across panels". Grant writing is truly an art. Something that I didn't truly appreciate before is that, as with any piece of art, each target audience has their own subjective opinions. I've had my lab for 4 1/2 year now and have written grants to DEB, MCB, and IOS. I've been fortunate enough to sit on preproposal and full proposal panels. One of the most difficult ongoing lessons I'm learning is that grants written to each of these are very different beasts.
1) Preproposals change the game. DEB and IOS require preproposals, MCB does not. I'll save most of the comments about pre vs. full proposals for other posts, but suffice it to say that writing a convincing preproposal takes a different skill set than writing a convincing full proposal. Since preproposals don't go out for external review, the fate of your grant is entirely influenced by the composition of the panel. In panels that get a lot of submissions focused on similar systems (at least from what I've seen at IOS where there are only a handful of well-worn symbiosis models) novelty can be a benefit. If you propose to work with a new/novel system, and the science makes sense, you can get some bonus points if every other grant is focused on model organisms. Furthermore, while there are certainly benefits to working with a model system, it's more likely that someone on the preproposal panel will know little details about the nuances of the organism and can call you out for poor experimental design. On the other hand, if you are proposing to work in a system that no one on the panel truly has expertise in, you better be able to convince them in four pages that the experiments are feasible. Depending on overlap of the panel's expertise with your own grant, there could be details missed during the preproposal discussion/reviews, and their will likely be subtle misinterpretations. It's just how it goes and feeds into the noise of the system. These things can be ironed out in the full proposal though because those will go out for external review. I get the feeling that DEB grants and review panels have a much higher variance in topic and system than IOS panels. If such a difference truly exists it definitely adds a new psychological layer into the process.
One last thing to mention in regards to the effects of preproposals. There is likely to at least be a little overlap between reviewers of your successful preproposal and your full proposal. I can't speak to anyone else on this, but when discussing full proposals I remembered the discussions surrounding the preproposals. I remembered perceived weaknesses and strengths and I tried to see how the authors dealt with these criticisms. I can't help but think that it's a good idea to dedicate some of your full proposal to laying out a response to your preproposal reviews.
2) Timing can matter for CAREER grants, especially since you have a choice about which panel to submit to. Submission of IOS/DEB full proposals occurs in summer and overlaps with CAREER award deadlines. Panels evaluating full proposals for both of these programs will also evaluate CAREER awards at the same time. Given the vetting of ideas that occurs due to preproposals, differences between CAREER grants and full proposals were often pretty glaring. It's also possible that you could have turned your non-invited preproposal into a CAREER grant, and that it would be reviewed by the same panel for both IOS/DEB.
In contrast, the normal deadlines for MCB panels that I've applied to are now in November. Therefore, if I submit a CAREER award to MCB there is no chance that the grant could be reviewed by the same panel that it would be as a regular submission. This matters because I've had some CAREER grants go to what I perceive as weird places at MCB (like Engineering panels) and they get evaluated very differently than they do at the regular November panels. Differences in criteria between regular and CAREER grants aside, the science may be essentially the same in the grants I've submitted but I get a feeling that there is much more variance in the CAREER reviews simply because the panel isn't quite the fit I imagine it to be. I think this also factors in because I'm not convinced that reviews of CAREER grants inform my writing of regular MCB grants (and vice versa), whereas I think you can get more traction out of reviews regardless of grant type at both IOS and DEB.
3) Funding rates are low regardless, but DEB (evolutionary processes at least, I can't speak to anything ecology) feels like an even steeper climb for microbiologists than for other biologists. The first few times that I had grants rejected from DEB, the POs made statements like "you have to convince frog biologists that your work is important". These comments were spot on and looking back I did a terrible job at describing how my work applied across systems. However, and I could be wrong about this although the few people I've asked back up my intuition, I'm not sure that grants from frog biologists at DEB get the reverse critique of "convincing microbiologists that your work is important". I'm not sure what this means, and certainly some great microbiology work gets funded through DEB, but it feels like there is a slightly implicit bias from the reviewers against microbial evolution work at DEB. There are some generally important evolutionary phenomena in bacteria (like rampant horizontal gene transfer) that simply don't apply across systems. Likewise, there are some generally important evolutionary phenomena in eukaryotes (sex ratio biases, diploidy) that don't really cleanly apply to bacteria. Given the broad makeup of review panels at DEB, I think it's just hard to get some types of microbial work funded through there even though in a world with unlimited funding it's the right place for it. It's possible that the reverse is true at IOS because most model symbiosis systems involve microbes.