1:700
Pro: Large selection of subjects, plastic or resin, a large number may be displayed in a small area
Con: Parts are small, most are waterline only (may be a pro or con)
1:350
Pro: Parts are larger & easier to manipulate for a novice. Most subjects are whole hull, Plastic or resin
Con: Limited number of plastic kits, mostly large subjects (Battleships, carriers) with some smaller destroyers & escorts. Resin kits cover many of the gaps (cruisers) and patrol craft. Many of the subjects are USN, or RN. Other countries are not as well represented.
Note that at first glance resin kits appear to be more expensive than their plastic counterparts. You need to see what is included in the kit. Many resin kits contain photoetch which is an extra purchase in plastic. Most 1:350 kits include PE, there are some 1:700 manufactures which do not.
My recommendation for a first ship would be either the Tamiya Fletcher or the Trumpeter England both in 1:350 scale. Pair them with the Gold Medal Models PE.
Reasons:
1) The parts are larger and easier to manipulate. If you choose to build a smaller scale later it is easy to transfer your knowledge down in scale.
2) Both of the kits are well engineered and go together well.
3) Both kits are rather small and have a limited number of parts. Larger subjects such as a BB of CV have numerous parts (avoids the OMG!, what have I gotten into factor). You can see the end of the project.
4) Both kits are relatively inexpensive when compared to a BB or CV. You are comparing 30 dollars plus 30 for the PE with 100 dollars plus 80 for the PE. Being less expensive also has the benefit of freeing you from worrying that you are going to screw up the big/expensive kit. The kit gets put away for fear of messing up and you do not learn anything.
5) The Fletcher has a relatively simple camouflage pattern, with a full size tamplate included in the instructions. The England is in a monotone blue camouflage. You can graduate to fancy dazzle patterns in later projects.
I cannot recommend the Trumpeter Fletcher, sold as The Sullivans, as a first kit. It has numerous issues, all of which are correctable with aftermarket, but you do not need to bite off than much now.
Build the Tam Fletcher or the Trump England. Don't worry about mistakes. You will make some. Learn from them. Then if you choose to go to a larger project (BB or CV) you have some experience. If you choose to go to a smaller scale - you have some experience you can fll back on. If you choose to go to a resin subject you have the experience. There are some kits and manufacturers which I will recommend to you if you choose to go the resin route. Do the Fletcher or England first