Having experienced Seneca II, Cessna 310, and more recently Aztec 'C' I would suggest for most uses Seneca II. It flies nicely, avoids Euronav, and is legally a reasonable load carrier. The 310 is a bigger looking machine and feels more like a grown up aircrfat than the Seneca which feels like a PA28 with two engines. As for the Aztec. Will carry antyhing. Is a big, thirsty, lumbering machine, robust and cheap to buy (but expensive to run).
In order Seneca II, Aztec, 310. Can't really comment on other twins at the low end other thant the tein comme which was my first owned twin. Loved it, great little machine but getting expensive to operate now because of age.