Hi! Quoting mr.James Murray, from onland.info site, a great place to learn conceptual and practical material about using Archicad: "SketchUp is a bad software that you should not use".
But in all seriuosness, you should evaluate what you want as a practice and then decide. Are you a more conceptual and vanguardist practice or are you more construction minded with down to earth design? If it's the former, SketchUp might be good for You (although i would use rhino better), if it's the latter, archicad will serve You better although You can also get very conceptual in archicad. If you do a lot of exterior work You might also want to take a look at Vectorworks, a step brother of Archicad.
If still in doubt, i recommend reading Mr. shoegnomes excelent post about what kind of practice You are or want to be. You can find it here:
http://www.shoegnome.com/2013/03/14/what-kind-of-architect-are-you/
Are You going to do only the schematic design and then delegate construction docs to someone else or are You doing all the work all the way? If it's the former, SketchUp might be good, if it's the latter, then archicad is a no brainer (you need put good effort into your archicad template though). You also have to take into account that importanting and exporting between these two softwares (AR and SU) is really good, so you can actually use both in diferent design stages.
Do You need super realistic rendering? Then SketchUp might be good because it has vray conection. If not, You can get great results within archicad or with twinmotion (which some people here seem to complain about, but ive had no problems with it and think that its almost a miracle of technology specially the 2020 version).
Do You need an integrated solution for 3d modelling and doing your architectural plans, sections, elevations and quantity take offs almost automatically? SketchUp has plugin solutions for this, but as You Will find in many forums, even it's users say it's a clunky and time consuming process and need really good equipement, but You can get spectacular results with good effort. Meanwhile, archicad can fly even in 5 year old computers.
finally, do You plan to remain a one man show or do You want to collaborate with other people and eventually grow? If it's the case, archicad will set You up for this.
Best of lucks in your desicion! but i suspect You already know the answer