Rectilinear creates unappealing discoloration on the surface of the parts.
Prusaslicer has monotonic ironing, I have no idea why BL removed it. BL obviously sees that it makes a difference, because it’s the default for top and bottom surfaces. Please put it back, ironing is imo unusable.
Are you sure they removed it? Maybe it was just added after they forked it.
Can you point to any documentation for that? As I am not seeing mention of being able to configure the ironing pattern, but rather the top layer pattern when they talk about ironing…
And then, there is still an open issue on the PrusaSlicer GitHub requesting that concentric ironing be added… 
I don’t know where this suggesstion stands, but I would like to give it a bump. I would like to see this feature added as well. Cura had it when I used Creality printers and I got cleaner results on my Enders with ironing than I do on my P1S. 
This is absolutely an option that needs to be available. It’s incredibly frustrating to have BL continuing to artificially limit their user’s options more and more on the software-front without first ensuring that they have the best option to meet those user’s needs. It feels like rubbing salt in the wound to provide concentric as an ironing pattern while omitting monotonic, the pattern that has been known for years to be the obvious choice for the best quality ironing results.
When first using BambuStudio and OrcaSlicer, I was shocked at just how many options, big and small they were missing compared to Cura, which had been my go-to. Now, without OrcaSlicer as an option, the available toolset has shrunk even further and BL doesn’t seem to be viewing their software’s shortcomings as a high-priority problem.
There isn’t really any “fix” to most of the missing tools in BambuStudio, as it’s just there and you can use it or it isn’t and you can’t. I would be hard-pressed to excuse BambuStudio launching with so many missing features/options, but to be about three years into its lifespan and still be lacking in such crucial areas when Cura and other quality slicers have existed as easy templates BL could use to get an idea of what tools and features they needed to offer from the get-go just feels beyond the pale. It feels as though BL decided to reinvent the wheel from scratch and has since decided that their three-year-old wheel, while still somewhat square, is so good that they can restrict any other slicers from being used with their printers.
Ugh. Rant over! XD