The Sheerline kit will serve you well, and builds into a nice model of the Type VII boat.
It's not the most authentic kit on the market (that honour belongs to the Hartshorn/OTW Type VII) but it's a heck of a lot cheaper, so the old adage about getting what you pay for applies here I think.
Sheerline, nee Eden ballast system is a good choice. It's failsafe and simple, with most replacement parts available off the shelf, so to speak- ideal for a beginner.
The modules/WTC's are also well built and sturdy- you shouldn't get too many problems with that.
One thing to bear in mind is that the Sheerline Type VII comes with some very prominent rivet detail moulded into the gelcoat.
These would look more in place on a Victorian steam ship than on a WWII submarine boat.
However, it wouldn't be such an arduous task to rub these out and reapply some more subtle detailing, after all most Type VII hulls come with no detail at all!
If you're not a purist, then none of that will matter.
One final word of advice- buy a APC/leveller it will enhance your sailing immensely.