How much larger are you typically wanting to make your files, and what output resolution are you intending to create most of the time (are you printing to Epson (360/720ppi), new Epson (300/600ppi), Canon or HP (300/600ppi)?
Ideally, you would be guided by the desire to get as close to one of those ppi levels as is appropriate with the minimum of resizing.
Knowing the percentage of files that you will likely want to upres, will help determine whether this should be a standard function of your workflow or an exception (and if an exception, to then consider where to do it - at RAW or at TIFF to reflect your process).
Ideally, in order of preference:
1. Print at the higher native resolution of the printer without having to upres
2. Print at the higher native resolution of the printer with minimal upressing (personally, I would scale to 720 from anything lower to 540 or to 600 from anything lower than 450 - YMMV)
3. Print at the lower native resolution of the printer without having to upres
4. Print at the lower native resolution of the printer with minimal upressing
5. Print at the lower native resolution of the printer having upressed using a method which you have determined to be most effective for quality having regard to the nature of your images.
That bring us to your question. If you're not upressing much (in terms of change of resolution) and not doing it often, it probably makes sense to do it ad hoc at the TIFF stage (but do it in an application rather than relying on the printer driver).
If you need to upres a lot - it may make sense from a workflow perspective to do it in raw. Then it's done for everything. However, you will need to compare the quality of the image once printed to that of a TIFF-based upres using whichever application you have to do so. In short, different raw files are processed in different ways by different applications and so I don't think anyone can make a blanket statement that it's better or worse one way or the other - you need a specific result for what you're doing with the tools you have.
I hope this is helpful on some level, to illustrate what I believe is the best approach to determine what you really need and the impact of workflow versus quality.