Why
THESE ONES of course!

Are you primarily playing EA and generally (or often) in UK tournaments? If so then rectangular bases sometimes may confer a play advantage as you can sometimes slot an extra stand into B2B by turning them sideways. That being said, strips, depending on how you orientate them, sometimes open yourself into being easier to be clipped. A round base by nature has no corners to be vulnerable to clipping more from one direction over another.
If you have an equal and or greater desire for these to also have a modeling for pleasure aspect and you're into the whole "scenic mini-diorama" base concept then the rounds do allow that to happen more / easier. Also some figures are larger than others and they can get a bit more room on rounds than strips while still not looking "odd" if you go with 4 vs 3 figures in he existing plinth holes (YMMV). I think it's "fair" to state the Iron Warriors stand is more aesthetically pleasing (I mean come on, cesspit!

) than the guard.
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As to which is easier to paint, I'd try and advise you to think of that to be a nonsequiter. STRONGLY consider instead using Popsicle sticks (or the like) to glue your infantry to (just use elmer's school glue as it comes right off) and paint them first, then base them. NOTHING worse to do than glue them to a base and then can't easily get a brush in there to hit details. (I'm a shittttty enough painter already to not need to make it harder on myself

)
There's a cost question as well. The OG strip bases are becoming slowly more expensive and rare over time. There are good equivalents but mixing them will probably be noticeable (though you might not be super overreacting OCD man like I am). The rounds are obviously in production still and in theory would be easier to deal with without worrying about hoarding enough for the future
just in case. Of course there's always the whole approach of making your own/buying 3rd party equivalents from the get go and only using those.
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