Vacuum Gauge - which one?

My VX has started to 'hunt' at about 3-4k so I think I need to re-sync the carbs, me and my mate did it last time which was fine but I do not think we got it 100%, so I'm thinking I would like to do it myself.

I have seen these at M&P for about £35, I know my bike only has two cylinders but its only a tenner more than the two cylinder version:



Or do I spend about £55 on one of this:



I have also seen a second hand Davida set for £50.



I know you get what you pay for, but how often would I use them? so on one hand I am thinking I should only spend £35 but on the other hand I am thinking I could get the Davida set for £50 and would probably get that back if I ever decided to sell them.

Or has anyone got a set they want to sell?

I'd go for the Davida one and sell it on when you've done with it, Well, I probably wouldn't really, It would sit in the garage forever! Just in case lol I'm shit at selling things   Have you thought about making your own DIY Manometer? It looks quite a simple task? but saying that,  it would probably cost more buying the separate parts than the loss of buying and selling a vacuum gauge.
http://www.triumphrat.net/maintenance-tips-and-tricks-for-the-t3-classics/228042-diy-manometer-carb-sync-tool-for-the-t3.html

I'm with Sim on this,the last owner has kept the instructions clean and the packaging,more than likely only used it once.

I have just spoken to the chap who was selling the Davida gauges and I got them for £40 plus delivery, he said they had been used about 5 times from memory and he has now got a ZX10 and will never uses them again. I am happy with that, they look in perfect condition but I shall have to wait until they arrive. I have just looked on the internet and the Davida System4 Gauges are about £150 new

You've got yourself a good deal there Andrew, you'll easily get your money back should you sell them on 

I did think about just getting a cheap 2 gauge set for about £26 and I think they would have been fine for what I need them for, but I do think you get what you pay for (within reason), with Christmas looming and 3 sons still living at home I could not justify buying the Davida Gauges new, in total the Davida's have cost me £44 so as you say Sim, I got a good deal, all I have now got to do if figure out how to use them!!

Well done Andrew,you can set your own little side line up now balancing carbs on bikes and cars,certainly pay it itself on your first use.