I'd say they are all good, comes down to what bells and whistles you desire and if you have brand loyalty.
A lot of wisdom in that statement.
In a small boat the 2 things I look for is displacement and weight. Since you have stated that your concerned about weight, why not an ordinary 2-stroke. As they are lighter and usually have more displacement that 4-strokes in that size range.
We (dad, brother, and I) never really have had to do any maintenance on our three small kicker motors, except cleaning the carbs due to ethanol, making sure fluids are full, change plugs once a year, and making sure that water is drain (full extent of our "winterizing).
Dad's 8 hp 4-stroke Johnson (made by Suzuki, a brand you left off your list) has been fantastic for use as a kicker motor for trolling, he often moves it boat to boat and runs it 300 or so hours a year. My brother's Mercury 4-stroke (5-hp), which he sold with his Lund, worked pretty good too. My 5 hp Honda, I believe will work well, once we get everything cleaned out from previous owner's ethanol use. Parts are expensive on the Honda, just the fittings for the gas tank line have been a pain (2 different Honda versions). Ours are all used for trolling so noise and fuel economy were consideration for the 4-strokes.
For thrust to run up river, I would be looking at 2-strokes. As your only running them for awhile. Also 2-strokes supposedly are easier to work on, especially for backyard type mechanics. As I said early never really had much maintenance but it is reported that 4-strokes cost more than 2-strokes in up keep.
