For work I’m flying 300-400hrs. I’ll have plenty of time to fly small planes. When I owned my cheetah I was flying 150hrs while flying nearly 1000 with work.
OK - Yeah, I'd honestly get the single for several reasons.
One - a single is more fun. Fewer levers, good handling characteristics, and ease of "flyability" are good things and fun things. I don't want flying "off duty" to be "work." I want it to be fun. Singles are fun.
Two, it's at least 2x more expensive to buy the twin, probably 3 times as expensive. For 150hrs per year in the twin, you could afford 450 hrs per year in a single - you could basically fly wherever you want for whatever reason and it wouldn't be a big deal. You could afford to fix anything with that kind of budget, and you could have nice glass and a decent autopilot. Beyond that, the performance between the two airplanes isn't appreciably different. It's not like you're picking up a ton of speed with the twin - it's only like 15 knots and maybe 150NM. At those kinds of speeds, you're going to want to make bathroom landings anyway - you're not going to slog it out all the way there.
Three, it's going to be possible but challenging to maintain proficiency in the twin on 150hrs per year if you're not spending time training in the thing, which adds to the expense. Honestly, you could take the cost savings and spend literally an hour or so a week on practicing engine out procedures in the single - you could buy this:
http://xavion.com/ and become insanely proficient. You could spend 50hrs per year on self study, and take the cost of 50hrs per year and spend it on aerobatics and emergency training with an instructor and you'd still be spending less than the twin. Finally, with controllability being significantly more difficult during an engine failure in the 310 than in whatever you're flying at work, there may be significant negative transfer between the two regimes. To that end, I'd recommend the simplicity of the single - especially if you don't see yourself spending the time (and money) to stay sharp on single engine work in the 310.
If you don't take my word for it, read this article:
https://www.aopa.org/news-and-media/all-news/2013/june/pilot/dogfight-twin-versus-single
In particular:
At a time of painful fuel prices, piston twins are anachronisms—and the open market judges them harshly. New Barons and Seneca Vs are produced in extremely low volume. And the value of a used single-engine Bonanza often surpasses that of twin-engine Barons of the same model year.
If you need to unload it later for whatever reason, I'd rather be trying to sell a Bonanza than a 310.
The only reason I can see to buy the twin is the "cool factor." If it's a status symbol thing, I get it, but honestly, if it were my family, I'd probably rather put them in the single. Statistically (hilariously), they're probably better off in the single as opposed to a piston twin.
Now if I could afford a King Air, then the equation changes...but yeah.
