Hi,
For this type of decision, it's not really a matter of better or worse, but a personal preference. I'm happy with having a non rechargeable battery that will not leak (although I did my work before rechargeable coin batts were available).
If you are getting a tech to do the job, maybe you can just ask him/her to take care of the details.
The diode is to cut the recharging current. If you use a rechargeable battery, you shouldn't use a diode.
If you like, you could compare the replacement battery's spec's with those of the original, to check that the recharge currents are within comparable limits. It's probably not an issue though, and a tech should be able to take care of that for you without much trouble. I think the computer probably has a current limiting resistor to control the recharge current onboard. If need be, maybe that could be changed to suit the new battery.
If you get a tech to do your work, make sure it's someone you can trust, as there are some gung-ho 'she'll be right' cowboy types around. Having said that, if you are into electronic hobbies, I would say it's well worth developing some basic skills and knowledge of your own. If you are going to do helli's, then and understanding of electronics, and soldering skills will help you there too. You can change motors and controllers etc. to give you that little bit extra, and for a much lower cost than what you can buy. Seeing as it is a hobby, and not a job, the time spent should be part of the fun, and it gives a lot of satisfaction in the final result.
