Buying a house ... Sell NegEq apt (& port tracker) or rent it out?

This is probably the most asked about topic on AAM, but I'll put our situation out there anyway and all help is greatly appreciated!

Have a 3 bed apartment:
- outstanding mortgage balance: €280k
- tracker interest rate: 1.1% + ECB (with PTSB)
- value: €200k - €210k
- possible rent: €1,200 pm

Want to buy a house, purchase price around €500k

Should we:
(a) Rent out apartment and buy house
(b) Sell apartment and bring the €70k - €80k negative equity with us

If we rent it out, we'll be paying the top rate of tax on it so once rental income is received, tax paid out, mgmt. fees paid, etc., we'd be down around €300 a month. Then for the house, we'll be on new business rates then for that mortgage with whichever lender we go with (around 3.8% - 4%). We'd plan to sell it as soon as the negative equity is reduced pretty much in its entirety or as close as - (in about 5 years time unless the market crashes even further).

If we sell it and bring the neg eq with us, we'll be paying 2.1% + ECB on the €280k and then 5.05% on the balance for the new house.

My head is wrecked from trying to weigh up the two scenarios so would appreciate an outsider's point of view. We really don't want to be landlords but we don't want to make a stupid decision either and capitalise on the negative equity unless it makes sense. We would plan on getting a property mgmt. company to sort out the rental property for us so that we don't have to deal with the day-to-day tenancy issues.

Thanks in advance!

There is no right or wrong answer here as everybody's situation is different. Assuming that you have the financial capacity to buy a new house and service both loans then your decision will be based on a capacity/willingness to service the shortfall on your mortgage over the longer term as a type of pension investment. BB's attitude is that the tracker rate is a significant benefit and goes some way towards mitigating the high tax you will be paying on the net RI. In addition property location and your view on the market are further issues.
My view is that if you can get the existing tracker rate applied to the new mortgage this would be a far better deal for you than carrying a new mortgage at 5% or whatever variable rates will ultimately rise to!! Have you addressed the issue of negative equity transfer with your existing mortgage provider?