Depends on what you want really, and how much you want to spend.I've just looked that Whisper up, and new (you need to compare like with like), it's 50 to 60% more expensive than the Peak (at it's £999 offer price). The spec is similar, Aliviio gear, Tecktro V brake (the Whisper has a disk on front). The main difference is higher battery capacity, depends how far you need to go on a charge I guess.
I think the Peak looks nicer, more like a mountain bike. The Whisper is more what the lads at work expected me to turn up on, (more sit up and beg, with a basket on the front is what they imagined) they were surprised when it looked so mountain bike like.
For me the Peak was mainly to go to work on, and got under the cycle to work scheme, which works out will have cost me about £680, and had 18 months to pay it out of my wages (tax free). So for that price it was a good deal, and I've actually been out on just 'bike rides' on an evening as it's such a nice ride. I probably wouldn't pay £1250 for it, I wouldn't for any bike most likely, I'd have gone back to a cheap motorbike, or just stuck with the car.
I reckoned on saving £10 a week in fuel would cover the cost of the bike over the 18 months. So it was an option for a new bike that pretty much pays for itself, and I've always fancied an electric one since I first saw the Powerbyke X24 years ago (the one with the water bottle style battery).
If in doubt, see if you can try a few out somewhere. I didn't have that option as our firm dealt with one company for all the bikes, so just took a chance on it, but have been pleasantly surprised (apart from not being able to us it yesterday, as I got up to go on it, and found the front tyre flat - first puncture I've had in ages).
I did have a try of
this bike at a caravan show before getting the Peak, and found it to be a nice ride too with a bottle style battery (26v). They also do another version with the battery behind the seat, that's 36v. But they're also very mountain bike styles, although the components are more basic spec than the Peak.