A question arose on the Twitts recently where a newish investigator wanted to know if it was wiser to push earlier for his/her first senior author paper in a ~3-5 IF journal or hold out for a ~9 IF journal submission. It emerged during the ensuing Twitting that the person had about 10 months of some degree of independent funding under the bridge so far.
My suggestion is, if you expect to have a career you had better have a good idea of what the standards are. So do the research. Do compare your CV with those of other scientists. What are the minimum criteria for getting a job / grant / promotion / tenure in your area? What are you going to do about it? What can you do about it? Don't misunderstand me- nobody is going to hand you a job / grant / etc just because you hit the modal publication numbers. But it will be very easy for you to be pushed out of the running if you do NOT hit the expected values. So do what you can to keep your CV as competitive as possible.
And this, really, is the starting point to my answer to @chemstructbio. It is absolutely critical to understand within your own subfield, within the pool of investigators whom you consider to be your peers, what the standards are. Particularly when it comes to Impact Factor. In my fields of interest, the answer to this question is going to be quite simple. If you have zero senior author papers from your lab, and you have been at it with funding for coming up on a year or more, the priority for a 3-5 IF paper is absolutely acute*. If this is in reach and a ~9 IF is a stretch of more than a single review cycle, do the lower IF one. Now.
The reason being the idea of balance, and the difficulty your advocates have making a case for you when you give them nothing to work with. A society level journal publication is respectable for all but the snootiest of assclams. Respectable. An advocate can work with this. Published data can be argued on the merits. It is very hard to argue with nothing.
Yes, yes, yes. We all know what time it is on the street and how long it takes to get to that first ass-kicking paper. But when you are sitting there with the Biosketch.....evidence is the thing. Evidence of a published, peer-reviewed paper. Not in prep, not in submission. Accepted.
Now, if you have one already....then it is time to start balancing numbers against the IF against the real impact of the paper. Then you can afford it. But if you have none, my friends, it is time to get one.
*This is not saying that you are hosed if you do not have a senior author paper. Not at all. It's just that it makes things go better. So if one is in reach, make it happen. It should be a huge priority, particularly if you have a little bit (or a lot) of funding in hand already. Because the reviewer demands for evidence of independent productivity will ramp up...clock's aticking.