You've highlighted the problem with the Specialist Units (and our flouting of the Trade Description Act). Although you've signed up to a unit that describes itself as having a commitment of only 19 days/year (Camp + 2x w/e), with the introduction of MATTs, you'll find that the commitment is now 15 days Camp (though my last one ended up being 23 days), 2 x MATTs weekends and at least one, probably two or more technical training weekends. Result - 21 days minimum.
Not appreciated by the Independent soldiers is that because Specialist Units recruit nationally, rather than locally, you may need to take a day off work in order to reach your weekend training.
Add to this the problems of recruit training. Because there is little opportunity to receive military training within your unit (a Specialist Unit's weekends concentrate on your specialism), your period as a recruit tends to be longer - three years is not beyond the bounds of possibility, and this is provided that you are available for the course dates.
It has long been recognised that Specialist Units are more appropriately recruited from among ex-Regular or overworked Independent TA soldiers (that is, increased responsibility in their civvy job prevents them attending drill nights and limits the number of weekends that they can attend). By this means, the recruit training element is complete before coming to the Specialist Unit. While this is the ideal, it doesn't work too well in practice for a few reasons:
1) there's an unwritten rule that Specialist Units can't poach from the Independents.
2) the overworked Independent will have developed unit loyalty and tends to jack rather than re-badge or have to make new mates.
3) it's actually harder to meet the Specialist commitments as they tend to be held on a one-time only basis - little opportunity to retake a missed weekend.
4) the Specialist is usually older than the Independent as he has spent time developing his specialism as a civvy prior to joining (you don't get many recruits under 22 - many are pushing 30) and so usually has greater work and family commitments when he joins.
Back to your original point - to be honest, it would benefit the Specialist Unit if you were to transfer to the Independents, achieve your recruit training and spend a year or so in a fairly concentrated military environment before returning to the Specialists. Also to be honest, if you were to go this route, I doubt if you would actually return.
So I won't be honest and I'll advise you to stick with your training in the Specialist Units. Once you've got through the recruit training phase, you can join the world of grown-ups, be treated as a human, look forward to rapid promotion and spend 15 days a year in somewhere "interesting."
I've done both and would find it hard to say which is best - they both have pros (cons fade with time) - but the Specialist Units need young blood so that, one day, the old buggers like me can retire. (Incidentally, I'm actually the youngest in my circle of mates, so we're getting a bit desperate for fresh talent).