If you plan on buying a compatible DS VC game and using Haxchi or CBHC, then there's no reason not to update to 5.5.2.
If you don't plan on buying a compatible DS VC game, then you need to find a game disc to update to 5.3.2-5.5.1. If you make it to 5.3.2-5.5.0, you can update to 5.5.1 using homebrew.
If you don't have access to a game disc with the 5.3.2-5.5.1 update on it, then buying a compatible DS VC game might be cheaper than buying a game disc.