tie clip / lavalier mic's are typically omnipolar, and pick up everything
at all angles
headband / neckband types like the Aerobic instructors use are
unipolar, and will reject sound off axis, which is correct for your use
as it happens, i am in the process of searching for a new system for a student,
and have been studying this particular unit:
these Samson small PA systems are Pro quality and this is their latest model,
lightweight , Lithium Rechargeable powered or plug in.. many of you are
transitioning to battery powered audio and this one is very competitive
the unique thing is to note the Wireless Reciever is a USB plug in, with an
accompanying USB port on one channel of the PA
this eliminates battery issues with the receiver completely, and is
a new wrinkle in PA systems.. i think this idea might catch on..
battery freedom is a great advantage for wireless in frequent use, while the
transmitter uses 2 AA batteries so you never have to worry about needing
a recharge in the middle of a gig, as AA's are dirt cheap and available everywhere..
many current wireless systems use tiny rechargeable batteries built in instead of
replaceable 9volt or AA alkaline, so i personally do not consider them Professional Level
also, if you look at used or old stock wireless, be advised most countries have re-allocated
Spectrum several times in the last decade or so, and many if not most older
equipment is now illegal to use due to interference issues
the distance you intend to roam from the receiver is also a consideration..
if you are a stroller as i am, you need wireless that will not drop-out regardless
of your distance or physical line-of-sight from your pa setup