I stayed at the Glo hotel when I was in Helsinki last year. I'd recommend it - it's right beside the Kamp, and you can use the Kamp's facilities like their spa and gym as they're under the same management. It's brilliantly located for ferry rides to Tallinn or wherever you want to go, it's a walking distance to shops and restaurants, and the hop on - hop off tour bus (if you're interested in that sort of thing) leaves from a stop 3 minutes away. Some tourist attractions are within easy walking distance, as is the nearest tram stop.

There is a sandwich shop opposite the hotel, which is handly as the food in the hotel is quite expensive.

If I visit Helsinki again, I'll probably stay at the Kamp as it's the more expensive of the 2 so probably nicer, but it'd definitely be one of these 2.