To some extent heaters are a commodity and it is a Ford vs. Chevy comparison.
Pentair MasterTemp and Starite heaters used a induced draft blower that introduces complexity and increased costs to repair.
Hayward H-Series heaters are natural draft without a blower. Parts service is ususalluy through pool store channels and youc an pay pool store markups.
Rapak is a Rheem company and most HVAC companies know their way around the units and can get parts. You are not locked into installation and service through pool store channels. Raypak has a good warranty for heaters purchased separately and installed by a professional contractor, not necessary a pool company.