I am setting up maintenance jobs such as CheckDB, update statistics etc.. I was wondering are there any disadvantages to using the CheckDB and Update Statistics job that are built in the SQL Maintenance plan wizard? OR should I create custom scripts for the job and add them to the SQL Server Agent? I am using SQL2008R2 and SQL2014 versions.
There's nothing wrong with using the Maintenance Plans. They don't offer much in the way of control, but they have lots of flexibility. It really depends on what kind of system you're trying to manage, how many systems, how big, etc. Those questions will determine if you need maximum power and control, or if simple automation is preferred.
since you are including CHECKDB consider the off-peak frequency for this maintenance plan as CHECKDB is an expensive operation. Also, check if you have any rebuild indexes (you should have one) then you dont need update statistics as rebuild automatically updates them. Depending on the version of the SQL Server and edition rebuild index can be done online (no interference to user's connection).