Broadening your horizons with planes is great, but boats are fun too. Unless time or $ is an issue, keep both. Things you learn in one will help you do better with the other. The Hobbico *star trainers are a good choice. Also good is to go with the ARF version you chose, rather than the RTF. This way you can select the individual components and end up with a better overall package, quite often at no higher price.

One thing you definitely should do before buying anything is to find a local club. That will be the place you learn from, and they may have a preference for engines, radios, etc. However, if you get a known trainer, not one of the cheap eBay things, and go with one of the major brands for radios (Futaba, JR, Airtronics, Hitec) and engines (OS, Thunder Tiger, Super Tigre, etc), you should be ok. The only potential issue would be buddy box compatibility.

Oh, and if you race boats, you'll be pleasantly surprised at how much less a gallon of fuel costs, and how much less a sport plane runs. A .45 size trainer plane can fly for something like 15 minutes on 10-12 ounces of fuel. My Sport 40 hydro burns nearly 18 ounces (of 50% fuel) in one 6 lap heat. Glow plugs also last much longer in sport planes.