I'm also a tractor newbee, but I've been trying to learn everything I can on compact tractors lately. Last week I ordered my first tractor, a Kubota
L3940/HSTC, with the gen 3 engine. My Kubota dealer told me the L30 Series had Generation 2 engine, the L40 Series has the Gen 3 engine, and next year Kubota is coming out with the Gen 4 engine. According to my dealer the various generations of engines have nothing to do with horsepower or torque, but rather how the engine handles exhaust emissions.
Reference the 3240 model. One Kubota dealer told me that some dealers aren't selling the 3240 model because this engine is on the boarder of not having quite enough power to operate certain attachments, particularly the 3240/HSTC model due to the additional weight of the cab and power requirements to operate the A/C compressor.
Based on what I heard about the 3240/HTSC (above) I was planning on buying a
L3540/HTSC but then noticed in the 3540 specs that it only has 28hp at the PTO. Several of the rear attachments I need require at least 30 PTO horsepower, so that's why I decided to go with the 3940.