There’s endless debate about copper core/iridium/projected tip variants. They all work and I have yet to see any advantage one over the other with only one suspected fouled plug in the last 20 years. The main variable is heat range and that is something that only your engine can tell you if it’s correct because it’s going to be affected by oil mixture, air density, fuel/air mixture, style of riding…. So if your BR5ES looks good when you eyeball it then it’s all good. If it looks hot then drop to the BR7ES. Despite few changes to the fundamentals of their engines Beta have recommended different variations of plugs usually in the NGK 7 heat range with the latest being the ridiculously priced NGK IR GR7CI-8 which is basically a BR7EIX for twice the price. Just like oils the recommended plug has as much to do with sponsorship as performance. I think the newest iridium plug recommendation is emissions based though as it’s not uncommon now for “off road” bikes to come with sealed carburetors and security screws on manifolds and such. Even the EVOs have different jetting now for “homologation”.