That very much depends on how efficient the visa-on-arrival system is. In some places (Thailand, for example) I understand it is relatively easy (I don’t need one, myself). However, I remember the utter chaos when Indonesia introduced it. We flew into Bali, had to queue up to get the forms, queue up to pay, queue up again to have the visa processed, and THEN join the immigration queue. It took almost three hours in all. They are a lot better now, but even so the rest of the family get visas in advance (despite them being more expensive than visas on arrival) just to avoid the hassle of joining an entire planeload of other passengers (and sometimes more than one planeload) all trying to go through a process that one can simply avoid
Incidentally – for any travellers from participating APEC countries – I cannot recommend highly enough the APEC Business Traveller Card. I have had one of these for years (as a permanent resident of Hong Kong despite being a British passport holder) – and I have to say that being able to avoid visa requirements, plus getting expedited immigration clearance (even in the US!), is worth the paltry fee dozens of times over. http://businessmobility.org/key/abtc.html
To answer the original question, though – I don’t think availability of a visa on arrival would make any difference to my decision as to whether to visit somewhere. If I want (or need) to go, visa requirements – however they are fulfilled – simply wouldn’t factor into the decision unless I was unable to get one!