Off-the-shelf software (generic CRM/billing tools) is faster to start using and often cheaper upfront, but may not perfectly fit your specific workflow — you end up adapting your business to the software's limitations. Custom software is built specifically around how YOUR business actually operates, which usually means better efficiency and fewer workarounds, at a higher upfront investment and longer build time. As a rule of thumb: if your business processes are fairly standard, off-the-shelf works fine; if you have unique workflows that generic tools can't handle well, custom software is worth the investment.