I think it is easy for hard techniques to seem more effective, 'cos they are easier to do more quickly. I think that is why hard techniques are often taught to armed forces, 'cos they learn it and then don't have time to think and reflect and practise regularly.
I also think that you can loose the point of aikido if you start off with a 'soft' form. It can easily lead to poor attacks, general lethargy and a non-martial attitude.
I think the best way is to start off slowly and firmly - trying to get effective 'technique' as quickly as possible. Then you try to improve the speed (without the injury). Then you try to improve the blending, and this is where your timing and co-ordination begin to improve and you can stop using lots of energy - luckily this coincides with you getting older! However it is very much a feel thing for the particular person. At the end of the day I think the technique should be effective.
Therefore, you have to be sincere to yourself, but there is a danger of thinking a technique is effective just 'cos you can crank it on if someone doesn't go down - you may as well be doing ju-jitsu. The ulimate and unattainable aim is perfect harmony; as chuang tzu said;
'once the fish is caught the net is forgotten'
(sorry for these constant chuang tzu references, he just seems to have a lot of good things to say).