(Army CSMs) Drill Sergeant duty or Brigade SARC?

Look at DA Pam 600-25, it will tell you what positions are recommended for career development in your MOS. Here's what is recommended for a 12B SFC for instance (notice that Drill Sergeant and Recruiter are both here but no SARC):
(c) Additional training. Basic Airborne Course, Air Assault School, Jumpmaster School, Ranger School, Pathfinder School, Sapper Leader Course, Rappel Master Course, Explosive Ordnance Clearance Agent Course, BSNCOC, Bradley Fighting Vehicle OPS and Maintenance Course, Basic Combatives Course levels 1–4, Mechanized Leaders Course, Master Gunner Course, Stryker Leaders Course, Counter Explosives Hazard Planning Course, and EOA.
(d) Special assignments. NCOs who are assigned as instructors/writers should be provided the same level of consideration as those NCOs who are selected for drill sergeant and recruiter positions. This is necessary in order to attract the best and brightest NCOs from operational units to serve as instructors for a minimum of 24 months.
Special assignments include the following: drill sergeant; instructor/writer; inspector general NCO; OC–T at a CTC (JRTC, CMTC, NTC); AC/RC advisor; ROTC military science instructor; EOA; career management NCO; BN, BDE, or DIV OPS; troop command (RC); State HQ (ARNGUS); RSC; or general officer command (USAR).
Nontraditional assignments include:
1. Rear-detachment 1SG. Many units have a SFC performing duties as the rear-detachment 1SG. These NCOs are challenged with performing 1SG duties with numerous unique leadership challenges.
2. Warrior transition unit. CMF 12 has SFC slots to fill within WTUs Armywide. These NCOs serve as platoon sergeant, with responsibility for 48 Soldiers, ensuring all Family and medical needs are met.
3. Detachment SGT. The detachment SGT is the noncommissioned officer in charge (NCOIC) of the military working dog (MWD) detachment. The detachment SGT directly supervises the kennel and detachment OPS, is responsible for all training, and ensures that MWD team’s proficiency is maintained. The detachment SGT has direct supervisory responsibility for the unit’s MWD program.

I know I am not a 1SG or CSM, however, I would honestly seek advice from my rater first and she what he or she thinks seeing as you are already slotted for school. My thought though is that the Brigade SARC would benefit you more than a three year tour as a Drill Sergeant, I may be incorrect. It's not a common school to be slotted for setting you above your peers and help the strength of your SFC packet....disregard your photo is with SSG rank not SFC.