There are a few 'which SIB' questions doing the rounds - the old lurkers will know this is the number one question and most of us advise the same old stuff, might be useful to sum up from the many years of topics a few handy observations:
1. In all practicality (capacity, convenience, compromise, UK seas) 3.1m to 3.4m is the size to go for (exception being the 3.8m Bombard Aerotec which really is like most 3.4s in practise).
2. Airfloor is much lighter and best suited to those inflating/deflating at launch, hauling up a beach, carrying on roof, packing in boot etc but may wallow a bit *even* with 100% correct pressure especially the larger sizes (very notable exception being the 3.8m Bombard Aerotec). With all airfloor SIB's pressure is *critical* - the last 10% in the floor especially makes all the difference.
3. Hard floor gives a much improved solidity and 'real boat' feel, is more hard wearing, easier to attach 'stuff' to, handles a bit better, is a faff to take apart/put together but the main issue is it will be *much* heavier and certainly with larger sizes really needs a trailer.
4. Flat floor, V floor etc: NO SIB will handle like a Searider - they just don't have the weight or deep V. In anything other than the merest ripples you will bounce about. General consensus is (forgetting the old truly flat floor Avon types) a solid floor/inflatable keel SIB is a slight improvement on an airfloor/inflatable keel. The airfloor Honwaves have a *slightly* more pronounced V than maybe a typical Zodiac/Quicksilver aifloor etc but deep it ain't. All SIB keels with the very notable exception of the 3.8m Bombard Aerotec (notice a pattern here
) are almost flat at the stern, the Aerotec is unique in that the V extends all the way to the transom and makes it ride/perform all on it's own and bridges the gap between a SIB and a RIB. It's still not a Searider though.
5. Engines: Two holy grail groups - the Tohatsu 9.8 2 stroke (weight 26kg), suitable for SIB's up to 3.4m, will fly with one adult, plane with two slowly, struggle with two and a half upwards. Then the 15hp 2 strokes - Mercury/Mariner (lightest at 34kg), Yamaha 15 (around 36kg) and Tohatu/Suzuki etc 15's.
The 8 to 10 kg of a 15 over a 9.8 makes a *real* difference when lugging it up and down a beach but a 15 will fly with two and should plane with three or four (if not too heavy) and add a couple of knots to the top end over the 9.8. Expect typical top speeds at WOT around 16 to 20 knots depending on combination. The above figures are all wide generalisations and dependant on the individual outfit - some kids/adults are a lot heavier than others!
If you have a heavier solid floor boat it will be a bit more sluggish. Small engine/small SIBs are very weight sensitive and may need distribution changes when driving to get best performance.
6. Which make? Plenty of great generic 'small brand' Chinese SIBs available (Honwave are Chinese and many others are cloned Honwaves) but a known big make (Honwave, Zodiac, Quicksilver, Suzumar, Avon, Tohatsu, Yamaha etc) may cost more initially but will certainly hold it's value much better and be much easier to sell. Many of us will have gone through two or three (or many more) SIB's before finding the ideal compromise for each individual's needs. Best advice (unless you really must have something brand new and know what you need) is to buy a used big brand complete outfit on eBay, dozens appear each week, you will save a packet over buying boat/engine separately and can always sell the other component on getting a very cheap boat or engine in the process. Buy right and you will not lose money when changing outfit. Example here:
http://www.ebay.co.uk/itm/1613030530...T#ht_63wt_1152
7. It's all a compromise!
Convenience/weight/cost/portability/handling/performance/capacity etc - all factors affect the others but nothing beats a SIB for the fun per £ ratio in the boating world.
,
Clewless
White Noise
) but it goes to show nothing much has changed in the advice given. 
