I don't think nor say that, if Alexander were introduced and supported as Nicholas has been in the past years, then he couldn't have the same profile as Nicholas. I don't think (and never said) that Alexander Hohenzollern can't be enough committed and promising as Nicholas.
Just, I think that there is a large difference between their situations.
Nicholas had the immediate and strong support of King Michael and Princess Margarita. This allowed him to have soon some visibilty. He quickly became rather popular and appreciated, partly for sure for his work and committment, but I'm sure also partly (and necessarily) due to the support he got from two respected and appreciated public figures in Romania.
Prince Alexander of Hohenzollern seems not to have any such support. Probably if he moved to Romania, learnt Romanian and engaged himself in various activities and charities in Romania he could became as popular as Nicholas, but it would take a far longer time due to the lack of visibility that Nicholas had thanks to the Royal Family.
My point is not that the Hohenzollerns aren't good enough for successfully becoming the claimants to the Romanian throne, but that they don't have the same visibilty and support that (some of) King Michael's descendants have.
And also I don't think that they will have it in the coming years. After King Michael's death his natural successor will appear to be Princess Margarita and not an unknown German distant cousin.