Both solutions are available and supported currently, though BCL Convert will be replacing bcl2fastq in the future. Illumina recommends adoping BCL Convert as the method of FASTQ production in customers' workflows, especially for those customers who require an on-premise BCL conversion tool.
Server Infrastructure: Single multiprocessor or multicore computer running Linux.
Memory: 32 GB RAM or greater
Operating System: CentOS 6 or higher
RTA compatibility: RTA v1.18.54 or later