Any time a manufacturer makes a lower end "entry" model, quality becomes more iffy, completely apart from design differences. That's generally true whether you are talking about Savage vs Stevens, Tikka vs Sako, or SPS vs BDL (or 40X), and includes any other type of product as well (GEO vs Cadillac).
Other than design and material differences, one major difference that's usually overlooked is manufacturing tolerances and the other biggie is quality control inspections. Where custom rifles have very tight tolerances and 100% QC inspections, lower end mass produced rifles have "looser" tolerances and often less than 1% QC inspections
That's why you can possibly get a low end product that's near perfect, but may also get one that's closer to junk.
As to the original question, bear in mind that until relatively recently, the very best high end big game hunting rifle manufacturers bragged about 1 1/2 moa accuracy, while most didn't mention accuracy at all.
For "normal" big game ranges (200yds or less), a 2 or even 3moa rifle will do the job just fine.
There's also the consideration that even most "dogs" can be fairly easily turned into at least "respectable" shooters with a little backyard gunsmithing you can do yourself.
If you like the look and feel of the SPS and it suits your budget, buy it.