I am in two minds about these brightly coloured plastic tubes. Yes they can teach pitch. Yes they are simple to play. Yes they are the same colours as the hand bells. Yes you can get additional chromatic notes and octavators to obtain pitches an octave lower. Yes kids love whacking them. So what are my reservations? Well simply, they sound crap. And to make a reasonable noise you need to whack them on something hard. And they always result in some behavioural issues. And some pupils just can’t cope with instructional activities with them, they just want to bash them as hard as they can. They are sturdy but not indestructible and they can bend if truly whacked. Would I buy them if I was resourcing a music room from scratch? Probably not, but I have used them in class, mainly because they demonstrate how longer tubes have a lower sound than shorter tubes. You can’t show this on handbells, keyboards or pianos, you can on xylophones but Boomwhackers are good to show this important concept. I have also used them to keep a steady beat and for simple ostinato work. I think if they actually sounded good I might use them more often.
So Boomwhackers or an additional xylophone? Get the xylophone.