The New Takanawa isn't that far at all from Shinagawa station, I would take the opinion of anyone saying that the walk is tiring with a large pinch of salt. (I was pregnant with Sacroiliac joint problems on my last visit and didn't think it was particularly taxing)
I've never stayed in or seen the rooms on the Club floor at the New Takanawa, but I do know they were recently refurbished just as the Superior rooms have been. The main difference seems to be that they are on higher rooms, have a better view and have Club access. I do know from the superior rooms that the photos on the hotel website are faithful http://www.princehotels.com/en/newta...oominfomation/
If you can get a view over the gardens you should also get a wonderful view of Tokyo itself on the higher club floors. Breakfast and some complimentary drinks and snacks sounds like a decent deal clincher. The quality of the furnishings for these revamped rooms is excellent.

I repeat that the Strings at that price is a very good deal. My only concern would be getting a room with a view into one of the buildings next door. (I just conferred with MrLapLap - neither of us are sure which we'd choose over the other. Bathroom at the Strings is much better, bed linen is fantastic quality, but then there are the gardens at the New Takanawa and the free breakfast and drinks.... tough one!)

As for the Pacific - I stayed here when it was a Le Meridien Hotel in one of the standard rooms. Hated it! Room should have been a half decent size, but it was stuffed with inappropriate furniture that made it feel cramped and cluttered. Bed was hard and uncomfortable too. I arrived after a 9 night stay at the IC Yokohama and wished I had gone to the Grand Prince Takanawa instead. I did get a shedload of SPG points for staying here, but as this hotel is no longer with Starwood there's no way I'd go back. It's a from me.